I don't recall Schiller even mentioning the computers in that timeline. I just recall the iPhone and iPod timelines plus the back to school stuff.
I think the iMac usually gets some sort of revision about twice a year, so it's due for some change. I don't think any sort of press conference is required for the next bump since it's not like the major changes the notebooks went through.
You might as well slap the MacBook Pro junk inside a 20-inch screen and consider that your next iMac. It'll probably have 4 USB ports (maybe just 3), FW800, probably MiniDP out, sound, power. Maybe the 20-inch screen is bumped up to 1920x1080, but probably not. DDR3, 2GB standard, $11,000 for an upgrade to 4GB (or $50 if you shop elsewhere), 500GB hard drive, 9400 in lower-end, option for 9600, everything else pretty much the same.
If a Blu-ray Disc option was included, I think I may mess myself. But that'll probably happen later in the year. With the good sales numbers I heard about for BDs, either Apple will cave by paying the "bag of hurt" licensing costs or Sony will cave by lowering them.