BUGS!!!! YES, legendary bugs (little strange, like: "OH NO! it´s the legendary ant!!").
serious now, I´d like to see what they did in the 1st gen, but with bugs (bug/fire, bug/electric, bug/ice, or anything more creative that includes bug/electric).
Bugs are extremely underated pokémon, but in the real life they are most times in 1st from the Most Extreme list (animal planet show) like the strongest animal, the most resistant animal or the fastest animal (attack higher than deoxys; HP higher than blissey and speed higher than deoxys respectively, why not?).
Dragon is too obvious and I doubt they´ll make them as the new trio.