Your post is really off the rails. Jesus DID NOT predict the sabbath would be kept by Christians until His return.
IN FACTJesus never used the word Christian at all. JESUS IS A JEW.
(King of Jews in fact - NOT pope or bishop of a church or head of a church. Jesus is the one and only annointed Jewish King, priest and prophet of ISRAEL. This is what Messiah, ha-mashiach in Hebrew, means. Google it.)
The word Christian only appears in scripture three times; Acts 11:26, Acts 26:28 & 1 Peter 4:16.
Some scholars have suggested the disciples of Jesus never called themselves Christians at all. The moniker was attached to them by pagans. (Acts 11:26) They 'were called Christians' not 'they called themselves Christians'.
Today the sabbath (shabbat) IS NOT KEPT by the church - either the Roman church, the orthodox church or the protestant church. This is a fulfillment of a prophecy of Daniel 7:25 (He [anti-Christ] will speak against the Most High and oppress his holy people and try to change the set times and the laws.)
The "set time and law" for the sabbath (shabbat) is the last day of the week - Saturday, not Sunday.
"the seventh day is a day of sabbath rest" (Exodus 31:15)
The Vatican attempted to change GOD'S LAW from Saturday to Sunday as predicted by the prophet Daniel.
We observe Sunday instead of Saturday because the Catholic Church transferred the solemnity from Saturday to Sunday.” (Rev. Peter Geiermann C.SS.R., The Convert’s Catechism of Catholic Doctrine, p. 50).
Thus the post-modern church DOES NOT KEEP THE SABBATH, called Shabbat in Hebrew, AT ALL.
Sunday worship, called 'the Lord's Day' by the Vatican, is a violation of the 4th commandment.
The attempt to change God's LAW is blaspheme - a SIN.
God owns Saturday.
The NFL owns Sunday.
One can argue against keeping Shabbat on Saturday, but one cannot rewrite scripture. What God has ordained is true. It is NOT subject to change by any human. God is not interested in human opinion. It is our duty to trust and obey Him and His LAW.
Unfortunately the post-modern church has fallen into the same trap as its Jewish forbears. It has created its own Tradition and assumed that Tradition supersedes God's LAW. It doesn't.
Behold the work of the anti-Christ - ON SUNDAY.
that's me, hollering from the choir loft...
None of which answers the objective facts of the OP. That the grammar of chapter 24 show us that Jesus EXPECTED His followers to be observing the Sabbath through the tribulation prior to His coming in the clouds and the gathering of the elect.
Each word emphasized in bold below is either a conjunctive particle or an adverb which connects what is about to be said to what was previously stated. Therefore the whole chapter is being answered in context to the tribulation prior to His coming and the gathering of the elect. They who are alive during this time period are therefore counseled to pray that their flight from this tribulation not be in the winter or on the Sabbath Day. Therefore Jesus expects His followers to be observing the Sabbath when He returns.
Matt 24:2 And Jesus said unto them, See ye not all these things? verily I say unto you, There shall not be left here one stone upon another, that shall not be thrown down.
Matt 24:3
And as he sat upon the mount of Olives, the disciples came unto him privately, saying, Tell us, when shall these things be? and what shall be the sign of thy coming, and of the end of the world?
Matt 24:4
And Jesus answered and said unto them, Take heed that no man deceive you.
Matt 24:5
For many shall come in my name, saying, I am Christ; and shall deceive many.
Matt 24:6
And ye shall hear of wars and rumours of wars: see that ye be not troubled: for all these things must come to pass, but the end is not yet.
Matt 24:7 For nation shall rise against nation, and kingdom against kingdom: and there shall be famines, and pestilences, and earthquakes, in divers places.
Matt 24:8 All these are the beginning of sorrows.
Matt 24:9
Then shall they deliver you up to be afflicted, and shall kill you: and ye shall be hated of all nations for my name's sake.
Matt 24:10
And then shall many be offended, and shall betray one another, and shall hate one another.
Matt 24:11
And many false prophets shall rise, and shall deceive many.
Matt 24:12 And because iniquity shall abound, the love of many shall wax cold.
Matt 24:13
But he that shall endure unto the end, the same shall be saved.
Matt 24:14
And this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end come.
Matt 24:15 When ye
therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand.
Matt 24:16
Then let them which be in Judaea flee into the mountains:
Matt 24:17 Let him which is on the housetop not come down to take any thing out of his house:
Matt 24:18 Neither let him which is in the field return back to take his clothes.
Matt 24:19
And woe unto them that are with child, and to them that give suck in those days!
Matt 24:20
But pray ye that your flight be not in the winter, neither on the sabbath day:
Matt 24:21
For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be.
Matt 24:22
And except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened.
Matt 24:23
Then if any man shall say unto you, Lo, here is Christ, or there; believe it not.
Matt 24:24
For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
Matt 24:25 Behold, I have told you before.
Matt 24:26
Wherefore if they shall say unto you, Behold, he is in the desert; go not forth: behold, he is in the secret chambers; believe it not.
Matt 24:27
For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be.
Matt 24:28
For wheresoever the carcase is, there will the eagles be gathered together.
Matt 24:29 Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
Matt 24:30
And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
Matt 24:31
And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other.