good question, I think that seeing all the armor permutations in the last few games and this will play 20 years later
(following halo 4 as last stand point as no one knows how it might change with 5 and so on...)
I think the base armor will all look like a newer version of the base armor mark 6, but with small differences based on the specialization.
As the armors get upgraded with new traits the armors can start to change more and more
for example, the melee (the one I will start with) can get a sword attached to one and later both arms that can fold out, so....