Opensolaris has gained support for the next SPARC processor which is likely to be named UtraSPARC T3. This processor extends the T-series processors to even more threads. Unfortunately, what Sun has mention about the processor so far contradicts itself so reports vary wildly.
There will be at least 128 threads and possibly 256 per processor, along with with multiprocessor support of at least 4 and possibly 8 processors. At a minimum, the top-end system will support 512 threads in a 4U, double the current T5440's 256. If there are 256 threads per processor and 8 processors, it will allow for 2,048 threads in a single mid-range SMP system. Although there are other systems with this kind of thread count coming, they will have price tags in the millions and have size and power bills to match.
However it comes out, it will be a wonderful consolidation box as it can be used to consolidate systems with a decent number of threads of its own. Many systems, esspecially SPARC, have used many threads for years and thus didn't lend themselves to consolidation on previous boxes except perhaps the T5440.
The chips will use at least four DDR3 controllers per chip allowing for huge DIMM counts and bandwidth. The processors are likely to ship at much higher clock speeds than previous T-series chips. Sun's target seems to be 2.1GHz.
I will post more information on these systems as it becomes available.