According to the End-of-Feature Notices, Solaris 11 is dropping support for older “legacy” SPARC hardware:

Support for legacy systems that have included the UltraSPARC I, II, IIe, III, IIIi, III+, IV and IV+ processor architectures (as reported by the Solaris ‘psrinfo -pv’ command) has been removed. All Oracle SPARC Enterprise M-Series Servers and Oracle SPARC T-Series Servers will continue to be supported.

Note: Oracle Solaris 10 will continue to be a supported operating system for these affected platforms as per the current Oracle lifetime support policy.