Actually I made a typing error. I meant MP2,1 which is the 2007 model name. This model was sold until spring 2008 and will run out of Apple care in spring 2011. So Apple by past performance will not obsolete hardware that is still in Apple care and k64 only OS X versions should not be expected before that date. If they decide to bring OS X 10.7 before they will most likely release it with k32 again.
I suggest that we find a common view about this issue so that advise to less experienced users is not clouded by a permanent discussion of when Apple will likely cease to support EFI32 machines.
I'm under the impression though, that Apple would still support the systems with the max Apple Care term, but exclude the K64 versions of the OS. They'd still cover the hardware, and the K32 editions of OS X.
But we don't know exactly when 10.7 will ship. IIRC, it took 2.5 years for Leopard, but just under 2yrs for SL to release (from ship dates, not announcements). Assuming 10.7 does drop K32, it may take longer to develop, especially as lean as Apple is running their code operations (as I understand it). So it could take anywhere from 1 to 3 years (depending on if it's only K64 <only drop K32>, and what features/refinements they may add, increasing development time needed). But if they can hold to a 1yr release schedule, they'd just not support that particular version of OS X on EFI32 systems, for those with remaining support coverage.
Assuming the work on 10.7 has only been going on for a month or so, 2010 is looking harder to do, given the short time available (i.e. announce in say June, and ship within Q3, likely Q4). But I'd think it's been on longer than that, given the number associated with the build (#47 in the articles out there). That still leaves a fair bit of margin (2010 - 2012; so as much as 3yrs, and figure around 2yrs is more likely, making 2011 more realistic).
I agree, it would be ideal to have a unified answer, but it's a tad hard to predict without further information. I guess given the avg of 2yrs - (2.5 on the outside) or so through the last couple of OS revisions, maybe we could settle for 2011 as a rough target date.