I guess it is all speculation because AMD isn't pushing Intel to release it on their regular time schedule. I believe if Intel hadn't already spent money on it and hadn't already promised it, they would scrap IB-E altogether. Here is something recent saying it had been pushed back to Q4 2013. Might be worth it for the OP to find deals on SB-E instead.
Ivy Bridge-Extreme Delay
I just built a socket 2011 system for myself, pretty much for the same reasons you want to. There are real performance increases when running programs that can use multiple cores and need to process large volumes of data.
However I basically just ignored any issues of upgrade paths. I am operating under the assumption that the compatible processors out now (Sandy Bridge-E) are all there will be for this platform. And in a real world sense these are powerful enough to handle anything out there. Intel has been more secretive that usual (if that is possible!) about their upgrade path, and most of what we hear/read is anecdote and rumor. There is no guarantee that Ivy Bridge-E will be released for socket 2011. But if they are I will cross that bridge then.
And isn't Haswell coming out on a whole new socket/platform? Socket 1150?
Intel does the tick-tock marketing thing. Tick is the incremental step, Tock is the major advance. I'm not sure if Haswell is the Tick or the Tock.
Intel has no CPU competitors now so they can do what they want, when they want. AMD has announced they will no longer try to compete in the CPU arena favoring GPU development.
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