Depends what you mean by 'make it', man. For me, playing regularly in the PL for any team is making it. But if you mean doing so for United, then that's a different story. Things can change rapidly and anything can happen, but gun to head, here are my takes on our current youngsters and what will happen with them in the next 2-3yrs:
Mason Greenwood - undecided. Needs a full season loan at a Championship club where he plays week in, week out.
Angel Gomes - sadly, I don't see it happening here. I predict he'll be abroad playing for the 2020/21 season onwards, probably joining a club of the level of say Valencia in the summer.
Axel Tuanzebe - yes. I think by the end of the season he'll be our established partner for Maguire. How long that lasts is a different story and depends on his progression.
Brandon Williams - yes. In fact, I actually think Brandon is in the most envious position of all our kids. Think about it - his competition at LB is an average-to-quite-good Luke Shaw who is ALWAYS injured and Ashley fecking Young. The iron will never be as scalding hot as it is right now for young Brandon - I hope he can grab it with both hands without getting burned.
Scott McTominay - yes with a clause. Any team with title-winning ambition would not have Scott as a mainstay in the 11. He's far too limited. 'Making it' for Scott will either be becoming the modern John O'Shea and spending 10yrs as a reliable, loyal, solid squaddie or joining the likes of Everton or West Ham by 2021 to be a first teamer.
Tahith Chong - no. I see Chong back in Holland next summer on loan, and that will become a permanent move the following summer. He doesn't have what it takes for me.
James Garner - undecided. See Greenwood, same situation.
Timothy Fosu-Mensah - no. Athlete, not a footballer. Loaned to the Championship in January, loaned abroad in the summer, sold the following summer.