SPARC is a processor architecture design that Sun (via Sparc International) licenses to others. E.g. [link|http://www.sparc.com/members.html|Fujitsu, TI]. Sun doesn't make chips.
If AMD were interested in SPARC, it could get a license to make the chips at any time.
There may be something to the rumor of taking Sun private, but it seems to me that if the main purpose is to do a reorganization then that could be done without the expense of a buyback.
McNealy needs to do something, but I don't see how SPARC fits into it.