Actually there's been talk of this since around spring/summer. And yes, it's only the headlining fights.
I think the main reason they're doing it is to make for more exciting cards, though I'm not sure that will do the trick. The thing is, a lot of headlining fights in the past have been contender shots, so a five-round non-title fight actually simulates the experience of fighting in a title fight. There have also been a few draws in the past few years that might have had a different outcome in a five-round fight, so I think that might also be another motivator in the decision.
If you want to keep up with MMA news, here are a few web sites that you can check a few times a week; some I check several times a day-
http://www.mmanews.com/
http://www.sherdog.com/
http://www.cagepotato.com/
http://mmajunkie.com/