Well, untill something faster than Firewire 800 is available, I don't think any of the non Power* line machines will get 800, like the Apple employee said it would decrease the difference between the PM and iMac, hurting sales of the more expensive machines.
What I expect in the next iMac... Hmm... switch to 2ghz and 2.3ghz maybe. Depends on where the PMs are then. If they PMs are lagging, we may only see 1.8ghz on the low end and 2ghz on the high end. (I'm betting on 2 and 2.3ghz, myself). Dual layer DVD burners maybe, or at least dual layer in the high end machine, and a faster single layer in the middle.
The video subsystem will be changed. Either a whole new GPU or they will stick with the 5200ultra for one more revision but go with 128mb VRAM. WHile I am hoping for a whole new GPU, I'm guessing the 5200ultra 128mb will be around for next revision, and they will change it for Rev C.
There may be a 23" model introduced at some point, but probably not the next revision, and maybe never. Who knows, though. (I'm guessing that it will be a Rev. C change, and will coincide with a new GPU). Im not sure the HDs will be changed at all. 80gb is pretty good for most iMac users, and I'm not sure I would see the point in raising the base to higher than that when the BTO options are there. I spose they COULD go to 160gb on the middle machine as well as the high-end, but...
They could also change vendors for the 17" screens, to go to a better specced display unit, but I think it's fine now, so why mess with it? (Others would disagree, I know).
I think it all depends on WHEN they upgrade the iMac line. If they do it soon it may be a smallish bump (1.6->1.8, 1.8->2.0, more VRAM, small price drop?). If they wait for Tiger to do it then it will be significant (1.6-2.0, 1.8-2.3, new GPU/more VRAM, 23" model introduced, dual layer burners, etc).
I'm hoping for a small upgrade soon, like in the next 3 weeks ;-) . I am going to be sadly disapointed, I know... But a small upgrade now would work well with another upgrade at teh Tiger release, so I can hope.
Rob