Early 2011, Sandy Bridge Quad-Core Intel 2800 and 2900 series i7 chips running at 2.3GHz and 2.5GHz, with 8MB of L3 cache. They will be the first Quad-core Mac notebooks and will be over 50% faster than the dual core models. Probably will be released by February 2011.
See this page for more info:
http://en.wikipedia.org/wiki/Sandy_Bridge_(microarchitecture)#Mobile_processors
Core i7 Extreme Edition, quad core (4 core, 8 threads) Core i7-2920XM, running at 2.5GHz with 8MB of L3 cache.
This is a 55W processor though, and Apple may choose not to use the 2920XM, and instead use the 2.3GHz 2820QM, which is also quad-core with 8MB of cache.
Apple hasn't used 45W CPUs in MBPs before. It's not impossible as it also has IGP which draws some watts but it's up to Apple.