I think it could be really positive. Just the fact that this option exists will re-orient everyone's YC applications toward thinking about making sure they've got the best team. I would presume that there would be a very high bar to be accepted as a group of founders without an idea. (I would also expect that with a high-potential team the problem would be choosing from a large number of potential ideas.)
This effectively opens the floodgates but it might also reduce the number of poorly thought-out ideas since teams now have a different access point.
Fits well with the 'replace university' comments in the PyCon talk.
edit: Makes me wonder how about the proportion of people who apply with demos (and how advantageous that is -- or is not).