Mega Pokemon have had an aggressive impact on the meta.
Average speed tiers have gone up, a notable example is M-Manectric with its Mega 135 speed (part of the reason behind the conception of OU- No Mega)
A pool of Wall breakers have emerged, such as M-Heracross and M-Gallade.
As for the future, I expect to see new Mega Pokemon (that are fully-evolved), but the concept of Primal Pokemon will likely be unique to ORAS.
The only non fully-evolved Pokemon I somewhat expect to see is Pikachu.