Here's an answer from Sumo Digital...
On the handheld platforms, we've not shown anything for a couple of reasons. Mainly it's been a question of making sure the framerate is sorted so any visuals we show are indicative of the final game. We don't want to show anything misleading, as if we have to pull back on detail or textures, you'd then (rightly) complain that early shots don't match the final product.
Let's hope that the final framerate isn't anything that causes hiccups during gameplay. Getting a bit nervous about this one!