Usually the official limits are far too conservative, and much larger cards will work albeit not as reliably. My first S60 device (S60 1st Edition!) had an official limit of 128 megabytes, but it worked with cards up to 1 gigabyte though it was a bit slow.
It may (or may not) have graphics hardware which would make it look a lot more impressive than the 5800. The N95, N93, N82 and E90 had graphics hardware with ARM11 as the main CPU.
If it goes over the $800 barrier as you predict (and I agree with you) it would have a very hard time making an impact beyond just technophiles.
The one thing it does mean though is that it would be very plausible for Nokia to do an OMAP3 Symbian device, and I'd expect to see them do it sooner or later simply to keep up with Samsung. Samsung has recently taken the lead technically with S60, they were the first to do an 8mp S60 model, the Samsung Innov8, and Nokia is now bringing out their own 8mp called the N86. From what I hear, Samsung knows that Nokia dominates S60 so they have to make an impact with real "standout" devices which get peoples attention.