I do beleive it is competing with the 5100. But as nikon and canon are always leapfrogging, be on the watch for a new dx a step up from the 5100.
Could have been the case when the t3i came out. But i feel the t4i is now tfying to out do the d5100, which it does in many respects. As someone else said, it fits between d5100 and d7k. It canon leapfrogging nikon. Its nikons turn next, hehehe....and I thought the T3i was the D5100's competition.