Well, the current trend has been going on for a while actually.. the wait times between Mac Pro updates get longer and longer,
In part that is driven by the classic Xeon workstation class product cycle getting longer and longer.
Intel's current roadmap has the mainstream desktop/laptop Haswell models coming out before the Ivy Bridge Xeon models arrive. That means Haswell Xeon models probaby won't arrive before Broadwell (2014) is rolled out. Maybe even after 2015's Skylake (if they run into any problems/bugs in Xeon Haswell and don't run into any major problems/bugs in Skylake).
The major problem with that approach is that 1/2008 release date for the 2008 Mac Pro. For those folks on a 5 year deprecation cycle are going to be itching to jump to new boxes (2008 + 5 => 2013 time to move). If Apple waits till August-Nov 2013 a very large fraction of those folks will be gone.
Similarity, any users that have run out of performance on a 2009 or 2010 model... they are leaving. The relatively minor speed bump of the 2012 isn't going to appeal to them. The 2012 has some traction against truely "old" (2008 and earlier) Mac Pros. 2009 models against 2012 is extremely lame because it is the exact same foundation/infrastructure.
The number of folks who "can't wait" is substantially increasing with every month. Waiting till August is almost trying overtly trying to implode the Mac Pro market base so small that it won't recover.
If Apple does a Sandy Bridge model in Jan-March 2013 and an Ivy Bridge model in Nov-2013-- March 2014 that would do far greater of repairing the Mac Pro market segment to healthy standing.
Apple would be "off" Intel's announce dates for new Xeon E5's .... but since there seems to be 3-7 months gap until they actually appear in volume it is actually safer for Apple just schedule to arrive "late" ... since Intel is likely to also.
What Apple needs to do is get back on a 12 (+/- 3) months regular schedule of Mac Pro updates. That way it is roughly predictable without explicit roadmaps. The frequency largely matches the other Macs.
but other than that I'm comfortable with the wait time. It gives me even more time to save up.
That's the issue. There is another very substantial number of folks who have already saved up and are ready to go.
In part, the 2012 release was an escape route for the 2006-2007 folks to move to. Waiting till 7-9 months after the majority of 2008 folks want to move is going to be a large blow.
Ivy Bridge Xeon E5 will drop into a Sandy Bridge board with minor firmware upgrades. It isn't like there is going to be a huge gap between motherboards in waiting for Ivy Bridge. It is the exact same core I/O support chipset.