Here is an article from today's Military Times online, If correct there will be a drawdown of 6 total USAF squadrons, the A-10's in units that recently converted from the F-16 bearing the brunt of the retirements. Of the six I believe it says one F-16, and an F-15 training squadron.
The USAF for better or worse have tried to retire the A-10 before. It was almost gone prior to the First Gulf War, but that was a no go idea then. The Army did threaten to lobby hard to take control of the aircraft if the USAF did retire it.
The A-10 is still a very survivable aircraft, but is slow, and does not have all the latest gee whiz electronic wonders (but it has been upgraded). I think the long and the short is they want money for continuing efforts with the F-35, and the dinero has to come from somewhere.
As far as the light attack COIN aircraft that has been in the news lately, 3-5 years ago, during the height of the recent conflicts, their was support in some circles for the turbo prop Super Tucano, or the AT-6 from Beech. It was envisioned as having 100ish airframes to outfit USAF units, as well as training units for those fledgling Air Forces out there that we are supporting. That was never popular with the "Fighter Mafia" as it is called in the Air Force. The requirement is now just for enough to provide for a training here in the U.S. to support these other developing Air Forces (Afghanistan/Iraq), plus onward sales to these countries.
Interesting times. Things do evolve, aircraft do get tired and worn out. But I think this has more to do with dollars than actual obsolescence.
http://www.military.com/news/article/af ... ESRC=eb.nl