^^ yes, this is huge! The only slow down then becomes regression testing in SQA.
This was the same with AVX and where has that brought us?
Benchpress, unless you're personally willing to recompile the software then it's going the way of every other ISA: 2-3 year adoption rate before we realize anything meaningful from it.
You're ignoring two key points here
1 - Nobody really cares much about the potential performance benefits outside of select workstation apps and server workloads, and as is the norm with those two segments, the software is optimized and recompiled on a regular basis anyway
2 - Software developers are lazy and won't recompile unless they can see direct profits from it. They certainly won't recompile for a very small percentage of the market
AVX2 will be supported by lots of multimedia applications on the day of Haswell's launch, or not long after. Just look at how fast SSE4 was supported, and that didn't offer anywhere near double the performance like AVX2 does!
That was a different era and even that was slow. If you want to relate it to more modern terms then take a look at AVX and its adoption rate. You'll see that it really hasn't been that stellar despite potential throughput increase.
Software developers care about money. Today most money made on software is made on ARM and not x86 (or at least that's the case for most users). The notion that developers will actually recompile because Intel has released this really sweet new ISA is crazy. If you truly do believe that then I've got a few investments you might want to take a look at
And there's an easy way to think about this -
When was the last time you paid for software or an application and on what platform was it? PC, phone, or tablet? On what platform do most users buy their applications?
The server and workstation crowd will adore AVX2, I'm sure of it. The rest of us, though, won't care nor notice.