Broadwell CPU will be for OEMs only; i.e. soldered into the mobo. However, Intel's Skylake CPUs (2015) will be "socketed" CPUs. However, they will not be compatible with socket 1150 motherboards; a different socket altogether.
There is no current information (at least to the best of my knowledge) with socket AM3+. Back in 2012 AMD pledged socket AM3+ will survive into 2015. However, their continuing financial situation may have changed that stance. Somewhat recently, AMD announced they will not continue the FX CPU series.
Whether that means they are abandoning socket AM3+ or if that simply means they will release a "name" line of CPUs for for socket AM3+ is unknown. Steamroller is the successor to Piledriver, however, so far it is only going to be released for socket FM2+.
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Not too long ago there was someone who posted a thread about wanting to upgrade his Core i7-920 from 2008 to either a A10-6800k or FX-8320. He wanted better performance and he did not want to pay "Intel Prices". I provided him with several CPU benchmarks for games using either the GTX 690, GTX Titan or Radeon HD 7970 depending on the game benchmarked. Those charts clearly showed that the A10-6800k (this year) was simply inferior and the FX-8320 (released in 2012) at best may only provide a marginal increase in performance. The poster then decided to Crossfire his Radeon HD 7870.
The moral of the story??? While the poster may have paid more for an Intel CPU at the beginning, it has saved him money in the end. Based on the performance of his aging i7-920 he simply did not need to waste money "upgrading" to AMD. Good thing he posted his question here at THG. Otherwise, he would have wasted money "upgrading".
My advice is to simply buy an Intel CPU. Either the i5-4670k, i7-4770k or the six core i7-4930k if you have $600 to spend.