For what Bulldozer does, it's fine. It's just too hot, and AMD will fix that.
I don't think there is any doubt that future *AM3+* processors will work on the socket -- the question is whether the OEM will support it on that model. You don't have anything to worry about with your motherboard, for instance.
I'm not certain your expectations of Bulldozer-Pilerdriver are realistic. Volts will drop 10-15% and performance will increase 10-15% in each core progression: Bulldozer-Piledriver-Steamroller-Excavator
The key step in the progression is Pilerdriver-Steamroller, which is 32nm to 28nm. The last 2 die-shrinks have not been kind to AMD, but they are confident with the half-node.
It's important to understand AMD Hetro-Compute
. The core design with Zambezi works, but ultimately, the core design will work even better with a SIMD Engine Array (GPU) and unified memory controller. The chip logic will compute C++/OpenCL across the most efficient cores, be they CPU or Radeon GCN cores.
Trinity, with Piledriver CPU cores and Turks GPU cores, is the third step in the progression to Kaveri
THE REAL FUSION APU
AMD is confusion
The 2013 Kaveri APU unifies x86 addressing for the 28nm Steamroller CPU cores and the 28nm Cape Verde GCN cores (let's guess - a cut-down
400?). At this point, I suspect, the Llano-Trinity-Kaveri APU Hudson FMX
line to generally equal or exceed that of the Bulldozer-Piledriver-Steamroller-Excavator AM3+ 990FX
series. Simply because of GCN compute.
But, wait. There's more
Your 990FX will easily take you to 2014, likely with Steamroller/Excavator, but what ultimately replaces the legendary series at EOL? Look to the Optys and their integration of 'Sea Island' GCN cores. I bet it has DDR4, too.