My thoughts:
B&M: less so due to saturation. An exception would be the Family Invert, which could potentially replace Arrow suspended coasters.
RMC: not that likely. There's room for conversions, along with new rides, but I think the relationship won't improve anytime soon.
Intamin: Zimmerman isn't over the rocky past with Intamin. That said, I cannot rule them out for a Ka replacement.
Vekoma: this new era does seem to be the next big thing. However, to me it doesn't feel like there are that many modern Vekomas right now.
Zamperla: after Top Thrill Lawn Ornament, I see them being restricted to flat rides, mice, and smaller scale rides.
Mack: it feels like this is the one that is going to be getting a lot of newer rides, with the extreme Spinners leading the way. Of course, this is just rumors at this point.
S&S: In terms of ride experience, I would love to see more of these. Unfortunately, with many of their coasters being problematic, I can't see anything more than 4D Free Spins at this point.
Some names you left out:
Premier: though AlpenFury is just the first new Premier coaster in legacy Cedar Fair parks (the others were Paramount era), I can see growth there. This includes potential retracking of rides like old Arrow loopers (not including mega-loopers).
Gerstlauer: Not many coasters as of now, and I don't see many coming. I'd love to see a 15 inversion Infinity Coaster one day. That said, does Hangtime at Knotts have a lot of downtime.
GCI, Gravity Group: not sure how to answer that, since wooden coasters often get maintained and re-tracked using their parts.
I'm not including SBF Visa (primarily kid/family oriented), Zierer (family oriented with two exceptions) Jinma (Chinese manufacturer with a lot of copycats), or Skyline Attractions (they earned this.)