I have a question...
If they could fit two entire regions onto Crystal, seven individual islands into LG/FR, and, on top of that, they fit Star Fox Command (with 9 different endings, awesome graphics, considering it's a handheld) and all those Super Mario 64 DS worlds onto ONE DS card. I'm pretty sure that they can make the Torn World as big as Sinnoh, with some of the older pokemon in it, on one DS card.
Think of them as a pseudo-sevii.
Jumpman, they could manage to do A LOT of things. The question is, why would they? That, and, do you know how long it would take to create a new world with new people and new graphics and such- and by new world, I presume that it would be in graphics comparable to the twilight in Zelda: Twilight Princess, it would have new or altered Non-Player Characters, and that most likely the wild Pokemon would be changed just about everywhere?
And what would be the point of going into such a limited pseudo-world anyway when you have the full Sinnoh in the flesh already?
It just is so illogical, its ridiculous.
Take my word-
it would be unique and interesting,
but it just won't happen.
Besides, a duplicate anything is just boring.
You should just hope for an extended torn world, like maybe a sidetrack comparable to Sevii Islands. During your first visit, it goes quick into the Giratina battle. Second and beyond- new world.
Hey, it's more probable than the other idea.