Yes… "all flesh"… Now since we know, or should know, that “flesh and blood cannot inherit the kingdom of God” (1 Cor.15: 50) then this must be a time when flesh lives on the earth. My opinion is that this is just after Christ’s return during the 1,000-year reign. I believe that there will come a time when there will be no more flesh so I have to look at that scripture based on that belief. Now the New Covenant is not between God and flesh but between God and His children who are the “elect” and they are not of flesh but of the Spirit. They, the children of God, the “elect” are not subject to the physical ordinances within God's footstool because they dwell above those ordnances within the Holy of Holies before the very throne of God in heaven, in the King’s chamber from where laws, decrees and ordnances emanate, where there are no sunsets and sunrises and full moons and new moons or weekly cycles.
Now at the commencement of the 1,000 year reign, after Christ’s return and the elect are changed into spirit to appear like Him and are glorified as He is and are crowned as kings and fellow rulers with Christ, those flesh who are left of the nations after His coming, the meek of the earth, those that “shall go forth and look upon the corpses of the men who have transgressed against [God]” will never be able to be at the same level as the "elect" because these elect (who at this time will be spirit) were called out of darkness prior to Christ’s return. After Christ’s return the darkness will be removed so those who live during the 1,000 year reign will not have to go through what the elect had to go through prior to Christ’s return when Satan ruled the world. The earth at the time after Christ’s return will be ruled by God and His elect.... from where law emanates... so all flesh that come to God during this time will go to a place before God to worship.... not as the "elect" previously did who came before their Father to worship Him in Spirit during Satan's rule. There is a strong indication by the scripture that "all flesh" who worship at this time will take part in old covenant observances:
“everyone who is left of all the nations which came against Jerusalem shall go up from year to year to worship the King, the LORD of hosts, and to keep the Feast of Tabernacles. And it shall be that whichever of the families of the earth do not come up to Jerusalem to worship the King, the LORD of hosts, on them there will be no rain.” Zechariah 14: 16-17
It was the above scripture that convinced me at one time to keep the Feast of Tabernacles, which I observed for 13 years along with many other Old Testament observances. Back then I didn’t understand the utter supremacy of the calling under the New Covenant. And I believe few understand its supremacy today because people either go back to mix in the old covenant with the New Covenant and still practice sinning (like I used to do) and use the New Covenant as a sort of eternal life insurance policy that assures them of eternal life in the future while they freely continue in sin in the present, or they exclusively observe the New Covenant for the same purpose.