I'm confident that the reason Autodesk has left AutoCAD to languish in the single-threaded, single-cpu world, is mainly because their long-term strategy is to migrate customers away from AutoCAD, to other products, and/or to the 'cloud' and more significantly, SAAS.
I agree with comments of JGGerth, PLawton and davea responding to this post:
http://through-the-interface.typepad.com/through_the_interface/2012/03/moving-to-the-cloud.html@ daveea:
Yes, in the 1960's it was called "time-sharing," and was a boon, in the days of batch processing via punched cards and mag tape.
@ JGGerth:
Although my ISP is generally quite reliable, I did experience an "outage" last year which lasted the better part of a work week, and was traceable to a problem with AT&T routers. AT&T are not my ISP, although in this case my ISP were entirely at the mercy of AT&T, and so was I.
SaS is a non-starter for me, for that reason alone.
As well, we use AutoCAD principally as a graphics platform which runs (extensive) third party ARX application(s). At the moment, I am anticipating the imminent release of an ACAD 2013 compatible release of the primary software with which I earn my living. ACAD 2013 itself, was of course released last spring.
It goes without saying that neither I nor anyone of my acquaintance can afford to shut down our businesses because Adesk chooses to "upgrade" their software (the underlying graphics platform) whilst the vendor of the discipline specific software with which we make our living has not "kept up" with the "upgrade," aka "breaking changes."