Since 1978, we have had the first x86 architecture (8086 CPU), and it kept changing since then. The question is: ¿why don't start a new CPU from scratch with the nowadays aknowledge?
I can't see the point of keep adding new instructions for that much time. I agree that SSE instructions and similar are really a good idea to have, but nowadays we have several aditions to a standard x86 CPU (SSE, SSE2, SSE3, SSSE3, SSE4, MMX, ...), so maybe it is worth making a new CPU from scratch with those functions built in, and even more. And possibly replacing the x86 paradigm having into account current computering experiences.
I think it will be good to have a talk with intel, amd, gcc developers, assembler programmers, and so on, to have a really good base for a new starting architecture, instead of keep adding new instructions to a deprecated (in my opinion) CPU type, and if possible, to keep backwards compatibility with x86 (just like AMD did with its x86_64 proccessors).
Of course, I am not an expert in this materia, but I think that they should simply drop the x86 plattform.. Any opinion to this will be really apreciated.