I think a portion of the hesitation to buy the current ones is the sense that they have been out for some time and concern over how long they will retain software support when they are finally replaced.
That's rather dubious stance.
1. Apple treated the 2006 as the 2007 as a bundle for "retirement" date. The minor bumped 2012 will likely get bundled to the 2010 as they are the same Mac Model number. If the current mac model number if replaced in 2013 then Apple's standard explicilty stated policy stands. Up to 5+ years after replaced on hardware.
http://support.apple.com/kb/HT1752
If the hardware is around why wouldn't it need software over most of the timespan?
You can look at some of the recent complaint threads about:
10.8 dropping 2006-7 Macs about 5 years after their introduction.
Recent bootcamp dropping support for 2008 Mac Pro about 5 years after their introduction.
Pretty good chance that 2008 Mac Pro will get dropped for 10.9 about 5 years after its introduction.
The only primary outlier is dropping PPC OS versions in 2009 after about only 4+ years after last PPC Mac release. However, this will likely be no where near a inflection point like the PPC->Intel transition was.
Apple has dung themselves a crappy support hole here if they follow their own stated policies. I would expect them to cut off the 2009 when they technically can in the next year or so; as if there had been a normal progression in the interim years. Apple is going to need to buy and long term warehouse spare parts in higher numbers than they usually do. But getting over quirky events is one of the reasons to have a huge cash stockpile.
These are probably more real at this point than software updates:
1. Tinker value as a box that can upgrade the CPU with a new one is disappearing since most users won't be able to get a new Xeon 3600 model for these boxes past September. ( Apple can buy longer but they are being pulled from the retail market this year. )
There is a used market for CPUs but that has higher risks. Especially if sellers aren't upgrading.
2. Similar issue over longer term with increased Memory costs. If high density ECC market shifts over to more profitable DDR4 production the current stuff will drop. The end-of-life price increase that hit pre-2009 models will kick in within 2-3 years.
3. For Apple to clusterf*ck the product management so badly as to see the product withdrawn from EU market is not generating much confidence there will later be "cheaper because replaced" 2013-2014 models. Few folks really wants to buy the "end of the line" unless absolutely have to because don't have options.
Alot of the mystery rumors about a super revolutionary new Mac Pro just add to this aspect. Although that is crappy product management too to let those spin out of control.
4. Most of all though the Osborne effect. Apple has heavily hinted new Mac Pro in 2013. The closer get to end of 2013 the smaller number of viable days Apple has to release the box. That means people will become more certain something new is coming and will stop buying to get a look at the new device.
Waiting longer brings more information and so increasingly larger number of people do.
For folks who don't closely follow the rumors between the EU Market withdrawal and upcoming NAB (or perhaps WWDC) conference there is some expectation that Apple will make a move. Or at least start doing controlled leaks. Instead there is a periodic Apple said something but we don't know anything articles the tech web bloggers keep dropping that just stir the pot (and generate ad views. )
so ive switched to a PC based system with win7 pro and ivybridge i7 3770k clocked to 4.5g 32g DDR3 2100mhz with an Asus Xonar Essence ST Sound Card with raid sata6 with OCZ vertex 3 drives, its fast and my music has never sounded so good.
