It's interesting to note that 20% of the companies have been working on their business for over a year (source: https://www.statwing.com/demos/yc-s12 ). Between that and the fact that YC is on record as looking for more clear-revenue companies, I think this shift will be more pronounced.
Another interesting note is that every major win (or apparent major win) for YC so far has had a very clear-- and very early-- revenue model (Dropbox, AirBnB, Heroku, OMGPop).