Last year the lineup came out in mid June. We pretty much had it confirmed that Refused, M83, and Beirut were headlining. It came later that The Faint was announced as the fourth headliner.
I don't really see any reunion act from this year's Coachella lineup as a real possibility to headline this year...
2011 - Death From Above 1979 played Coachella and headlined FYF
2012 - Refused played Coachella and headlined FYF
2013 - Wu Tang = Too big of a name / wouldn't happen anyway. Nick Cave = Too big of a name. Although I do see The Postal Service as the most likely reunion act to possibly headline, I don't think it will happen.
In my mind, Sigur Ros is a candidate, but they are rather popular compared to previous headliners. I'm sure Jawbreaker will be offered a spot, but they will almost definately turn it down. They would have surely been offered bigger money for Coachella. Godspeed You! Black Emperor would be amazing, and they are possible. Grizzly Bear is also up there as a possibility.
Each year, it has seemed like the headliners have gotten bigger and bigger, but for an indie festival, anything bigger than M83 is pushing it.