The Logical Domain hypervisor for Sparc T series processors, known formally as Oracle VM Server for Sparc, is probably one of the best technologies created by the former Sun Microsystems for its homegrown servers. (Solaris and ZFS are two other key technologies.) Oracle has just kicked out a 2.2 release that makes LDoms more …
Increasingly skeptical of M4 being Oracle
The new Hot Chips program, posted a few days ago, mentions a 16-core "SPARC64 X" for the "next-generation UNIX servers." This would seem to imply that either M4 is actually a Fujitsu processor, or that Fujitsu's going to keep making its own CPU's for its own Solaris servers without Oracle on board.
sun4u -> sun4v migration already supported
You can already move workloads from sun4u to sun4v (and the reverse) with FLAR images..
This is well documented.