"SPARC64 X; Fujitsu’s new generation 16 core processor for the next generation UNIX servers
16-core SPARC T5 CMT Processor with glueless 1-hop scaling to 8-sockets"
The SPARC T5 is expected to be built using 28nm technology and double the number of cores compared to the current T4 processor. The Sun Oracle server line should also include a 8 processor version, T5-8 which will then be have four times the number of cores (128) compared to the current T4-4 (32).
This session will be held August 29, hopefully more information will surface afterwards. Otherwise it would be a safe bet to say that we will know more about the SPARC T5 after Oracle OpenWorld in October.
The Register has an article about both the T5 and the M4: Drilling into Oracle's performance boasts.