I don't know the answer.

I have heard that Sun will support a version of Solaris on a SPARC system for the life of that Solaris release, but I can't promise that it's true. What I can do is point to some locations that will have the latest information.

To find out which SPARC platforms currently run Solaris 10 (or OpenSolaris), go to the HCL:

BigAdmin HCL

You can also get a quick summary from the Sun documentation:

Solaris 10 Hardware Platform Guide

For general requirements and specifications for Solaris 10, see:

Solaris 10 System Requirements

-Rick