Oh god please dont make groudon and kyogre mega evolves,
pleas
Personally, I wouldn't expect that.
I won't be too surprised if a few more pokemon end up with Mega Evolutions, but I don't think they'll Mega Evolve the legendaries.
They didn't do so with Yvetal and Xerneas, and they were
the opportune legendaries to do it to.
So, it would seem a little bit weird to go back and give these two a Mega Evolution.
I can't overly recall from the last remakes, but do any changes in a remake count as a retcon?
Because I definitely can't see them retconing it so that the legendaries were always supposed to be Mega Evolvable.
That is of course if this is a straight up remake (ignoring the 3D design aspect), and not just a revisiting to the region.