Relax and take a deep breath, don't spoil the fun.
Gosh Don't be too excited over 5th generation. It will come out, says the pokemon anime staff. If you become too excited, you will not be able to resist the also inevitable 6th generation of pokemon when 5th generation comes out.
Let's not make fanciful ideas lest our image of new pokemon is shattered! But still you could discuss the plot.
I think that there will not be world domination this time, however, i think they are making another pokemon with the same purpose as Arceus, so that there will be 2 pokemon religion, one being with Arceus and one being with Pokemon X. Then the 2 religions will fight in an epic battle with trio legends.
Proof for no evolutions of pre evolutions for the next generation:
Generation 1: Professor Oak studies pokemon habitat
Generation 2: Professor Elm studies pokemon breeding, which in turn came out breeded pokemon.
Generation 3: Professor Birch studies something akin to professor Oak, thus the pokemon were mostly indigenious with a few exceptions such as azuril.
Generation 4: Professor Rowan studies pokemon evolution, thus came out many different evolutions and pre-evolutions including breeded types.
Generation 5: Professor X studies pokemon y (my guess is pokemon biology), thus the pokemon might be indigenious to that area again.
If I am wrong, just call me an imbecile... LOL