What chip manufacturer do you work for? Windows 8 128bit in 2011 might be a bit ahead of it's time. Then again you never know. Maybe 10.7 will have a stable 64bit platform by then.
You don't realize how silly your question is, do you? Or did you just leave off the smiley face?
Intel's roadmap through 2011 is public - no 128-bit CPUs on it. (I know more detail through Intel NDA disclosures, but that doesn't change my stance.)
What is the sole force driving the transition from 32-bit to 64-bit - it is the fact that having a 2 GiB to 4 GiB address space per process is too small for the leading edge applications today. (It's not a 4 GiB per system problem, we've had 64 GiB support for systems for many years.)
64-bit raises the limit to 16 billion GiB.
Dell is selling dual Xeon workstations today with 192 GiB of RAM. Nice, but the CTO addon price for 192 GiB is $207K.
So, 64-bit is good for a system with a memory cost of $2.4 trillion dollars in today's money. Let's take an absurdly optimistic estimate that memory prices decrease by a factor of 10 each year - that means that in 2011 a 64-bit CPU could address $24 billion dollars of RAM.
As I said, you don't realize how silly your question is, do you?
(I'm ignoring the issue that electrical and timing issues limit a system to a small number of DIMM slots. Assuming the 64-bit limit, a system with 16 DIMM slots (a very high number, by the way) would need 1000 PebiByte (1024 petabyte) DIMMs.)