AMD going APU only doesn't mean they will drop all of their AM3+ chips, however. They have said that they have no intentions on competing with Intel for the CPU speed wars, and they've also said that the AM3+ infrastructure will be around for "years to come". This tells me that whatever the next chip is -- Steamroller-based or Enhanced-Piledriver-based -- AMD will still have chips with >2M designs available to people who want them.
I was never implying that by going APU-only, AMD will literally just abandon everything else and stop selling it. It would be a marketing disaster and the shareholders wouldn't be too pleased either. Going APU only just means that they will focus mainly on APU's and no longer bother with normal CPU's, unless they migrate the FX line over to FM2+ as the unified socket strategy would suggest. Even so, going APU only with Excavator would be well over a year from now, as Carrizo won't hit until c. 2015. HSA will have gotten at least some traction by then. I don't think the company would invest so many years (this has been an initiative since 2006) into this concept if they weren't absolutely sure it would take off for them.
Also someone would have to be daft to compare an APU to a discreet Haswell/Broadwell octocore. This is Intel here, they won't released any octocores for cheap when their current hexacores cost well over $500 already. AMD will maintain their Kaveri APU's for people who want to be HTPC's, budget gaming rigs, or just want better CPU performance per core with the new uarch, and simultaneously maintain their AM3+ platform for people who want those 3 or 4 module-based parts. AMD would never drop their FX dies when they have an upcoming API (Mantle) that will increase CPU performance by removing bottlenecks, as well as most engines that support said API being optimized for eight threads already.
As for me, I would be perfectly fine with a Kaveri quad-core part. For what I do, I don't really need any more cores. I wouldn't mind a three-module SR part, but if it ever comes, I'd just upgrade to that, but I doubt it will exist. Another goal of HSA is offering mega-increased compute performance while also decreasing power consumption. Sure, you drop in an i7-3960x and a 7990, and you're gonna get some nice compute performance, but you're also gonna use lots of power to do so. A lot of companies want low-power designs for these types of things. Not that I keep up with the server side of things, but it seems that's why there is the Berlin APU and why Warsaw will use "enhance PD" cores to improve performance while decreasing power consumption.