I mean we won't know for sure until closer to the next film, but with the things I pointed out I doubt they'll be forgotten. Honestly, I think the only robot character known to be alive who has a reasonable chance of not showing up again is Brains, and I'm fine with that either way. If he shows up again, then cool, but if he doesn't, well let the little guy enjoy his freedom away from the action. One thing I do think is that TF 5 and maybe TF 6 as well is what will make or break the Dinobots. Anyways, I'd guess that the big things for TF 5 besides Prime's search for the Creators will be the restrengthening of the Decepticons under Galvatron and the Dinobots versus some new, giant Decepticon(s).