No, he hasn't. The differences are negligible and it's purely cosmetic, but they tinker with it film to film. And it's not even a particularly big deal, but I guess that's sort of the point - it's so minor and it's not even worth explaining on-film as an upgrade, there's really no reason to do it, other than the high-end figure companies get to put out a new cool variant. Steve could be rocking the AoU suit in CW and IW and you lose nothing.
Guys like Stark are constantly tinkering tech-wise, updating, upgrading, prototyping, and of course that's absolutely a part of the character. Guess Cap's just more the Indiana Jones type - he doesn't give a crap what he looks like, so as long as the suit's functional and proudly flying the red-white-and-blue there's no reason for him to change it. Iconography and his trusty shield, boom, good to go.
I sorta just see Robocop more that way. Updates of new tools & weapons along the way as OCP thinks up new stuff is just fine, like the hand-spike and stuff, maybe a secondary gun somewhere, or something else police-y like some ultra-strong riot shield type of thing. But given this is the same continuity as Verhoeven's, I just want the broad big-picture look to be way closer to the original than the Kinnaman flick. Helmet and torso should be identical or close-to, at least, and it should all have that same bulk. He felt way too limber & quick on his feet last time around with the reboot, and just too "every other sci-fi robot ever".
And yeah, Guard, Neill's Detroit should be a hoot. Hope he doesn't go too futuristic though, it should all feel kinda 10-15 years from now tops, basically just ultra-modern but still loosely "present". Hope they actually shoot in Detroit this time around too (did they for the reboot? can't recall), think the originals were Texas from memory. It'd be nice throwing some jobs Detroit's way for this, all they've been through.
Starlord, Burke wasn't really the problem with 3, it's not like it would have been magically a great movie with Weller with the same script. And hell, 3's still a blast, that's a fun movie just in a whole different way. Bad, but fun. I actually really enjoy the hell out of 2, even with all the "why is he all robotic again?" nonsensical stuff. That's a brutal movie too, disturbing and hilarious at once.