You will also be able to receive Pokemon from the GTS that are not yet in your Pokedex,
Oh, thank forget for that.
That makes me unbelievably happy.
There was absolutely nothing worse than playing Pokemon Black, and finding out that Rufflet (A White exclusive pokemon) can not be seen in-game, and therefore can not be requested for or searched for on the GTS.
Meaning you HAVE to know someone who owns a copy of Pokemon White, or you have to purchase your own copy (and a second DS, if you don't have one).
And I so hope that they put in some safeguards and restrictions on the GTS for illogical or impossible trades.
Or at the very least, let you see more than just 6 possible trades which will always appear and can't be ignored in the hopes of finding an actual trade.
And while I'm there, it would be really really great to have a Search for Wanted feature.
Input a Pokemon Species, gender and level-range (or none for the last two), and see what people are willing to trade for it.
It would make it much more easier for people if they knew that they already had something people wanted, rather than searching for Pokemon to recieve only to find they have none of the pokemon wanted.
I had to do whole series of trades, and breeding in order to get 1 Pokemon on the GTS before.
Bloody git wanted a Snivy, and I chose Oshawott as my starter.
No one was trading Snivy's for logical things, so I had to go and get a Serperior, after getting an Eevee for that trade. Then bred the damned thing, and by the time I was done, the bloody trade was gone.