Depends on what you mean, but it's reasonable to expect exo-suits with upgraded armor packages since they can handle the extra weight. Fallout tier stuff? That's probably the closest to legitimate power armor of the three images you provided.
40K? Maybe in 39 thousand years. Again, 40K has some fundamental issues with the way power armor works since, basically it's magic. 40K power armor exists to look cool and nothing else.
Halo? Kek, no. Halo is gay and dumb.
What we're most likely to see is exo-suits for the legs and core to permit a soldier to carry more gear(or carry the gear they already have for longer), a more expansive information package, and potentially, if there's any room left, more armor.
There's one very important thing that 40K gets while Fallout and Halo(still kek) fuck up - ceramics. If there is going to be more armor, it's almost 100% certain that it's going to be ceramic based within the next 50 years or so(unless they figure out some way to use carbon nano fibers or tubes for that).
Why AT rifles? A simple .50 cal would properly suffice but that's not the problem. A .50 cal will go through a regular soldier just like a PTRS will, the reason to adopt power armor is how much more you can get out of an individual soldier.
In the end the closest we're likely to see to power armor is going to be something like armored CBRN suits. See pic related for most realistic power armor in any game.
>mechs
>with arms
Highly unlikely. If we do get mechs, which while unlikely is possible, they almost certainly won't have arms(because why would they? It's added weight that does absolutely nothing when you can have a rack of 8 ATGMs and a cannon for the same mass).
>>626808
>space combat
>boarding
Literally never in 10,000,000,000 years. You're retarded for even thinking that's a possibility.