They will be permitted to ENTER the MK age because, 1) they will have been "INVITED" (during the Trib yrs), and 2) provided they will have ACCEPTED that "INVITATION"... but recall, it (their being "INVITED") will be DURING a time of GREAT DECEPTION and GREAT PERSECUTION (i.e. during the TRIB years)...
... these Gentiles who survive the trib years are shown (as "STILL-LIVING" persons) in the separation judgment of the nations / Gentiles: "the Sheep" [/righteous] being called "ye BLESSED" by our Lord, and "the goats" being called "ye CURSED" by our Lord (whereas "the least of these My brethren" [third element, BESIDES the Sheep and goats] vv.40,45 are not the ones BEING "judged / separated" in this particular judgment; NOR are they "the Church WHICH IS HIS BODY" [who will have been "raptured" out WELL-BEFORE this point in the chronology])--
so "BLESSED" and "CURSED"... sound familiar from another text of Scripture??
Major clue as to "who" these "least" are, in vv.40,45 [the believing remnant of Israel!]... and to have "aided / blessed" those particular ppl, who by the way will be the ones to CARRY FORTH the "INVITATION [message]" [during those Trib yrs of GREAT PERSECUTION, for them] will have put those Gentiles at great risk to themselves, as well...)
yup, that's correct