X/y definatly should have some DLCs. But they really need to add some true content.
A whole new route. It is filled with though pokemon trainers and there is a legendary pokemon at the end. In addition, about 12 new non legendary pokemon are catchable on this sidequest New run in with with team rocket,
A three part DLC, each part is a different dungeon full of team rocket grunts, each part has 12 new non legendary pokemon you can obtain, No legendary on the first two, however you face a big team rocket boss and earn a new TM for defeating him/her. In additon you may get some help from a famous pokemon trainer like Lance.
the third part has an encounter with the new boss of team rocket and mewtwo at the end, and you can unlock a new form, Metal Mewtwo. If you have bought all three parts you can also get a mew.
A new safari zone. Once again new pokemon including some fairy, dark and dragon types to find. The safari zone needs to feel special again, making it DLC with new pokemon would do that.
New Starters. You travel to a island, and get to choose from three starter pokemon, After you pick one, You have to enter a forest and explore looking for a hermit at the end, Hte Hermit will test your bond with the pokemon you picked in a battle. Battling him should be alot like doing the first gym. New trainers, and about 10 new pokemon are in the forest, not counting the starters.
Bottom line is, while DLC can have new legendary pokemon, it needs to offer more than just a legendary. We got event legendaries for free before, It would be milking the fan base if we all of a sudden had to pay for them.
If there is a 3rd version form pokemon black and white I will close my account.