Very possible, but it begs what they'll do with the "evolution" legendaries, to make them worth the evolution. Will they treat these EX pokemon as basics as well, as some previous sets have, or what can they do to keep them competitive. Our current EX pokemon are pushing 180 HP, higher than any stage 2 in the format right now. If we were to get a Magnezone EX, or a Garchomp EX, or something similar, we would either be looking at over 200 HP, or some sort of ability that makes them warrant the extra trouble of evolution.
I like how some of the EX are proving to be worth two prizes, unlikes the early versions of the original ex and the majority of the legends, but I haven't the slightest idea as to how that will work out with an evolution, and especially a stage 2 line.