There would be no point to this, the 'instructions sets' of which you speak are just registers and microcode that are re-rolled into newer features.
You're really referring to extensions to the x86 instruction set.
Intel tried this with IA-64 (Itanium) and very few people bought it due to a lack of software being available for the new (totally different) instruction set.http://en.wikipedia.org/wiki/Instruction_sethttp://en.wikipedia.org/wiki/X86x86 processors have been internally RISC and externally CISC (instructions from memory) since the Pentium Pro era of ~November 1, 1995. The AMD K5 could probably also be considered part of the 6th generation of x86
RISC isn't new.
ARM is 'new', I doubt they have half the registers of an Intel or PowerPC processor though.
- More registers == better performance (usually).