You think they would. But remember there was a time when 64 was a ton of memory (more then most people). Then 128, then 192, then 256, then 1gb, then 2gb, now 4gb.
Like 16 will be a big deal when each 2/4 gb stick is $100.
It is inevitable.
Heck, my 286 was the bomb because I had 2 Meg of Memory.
My 486 rocked the world with 8meg of ream.
I oversaw a massive deployment of corporate desktops recently with 512mb.
My current PC has 2000x more memory than my 1st PC, 500x more than my 2nd, and 8x more than many entry level systems now.
So yeah, give it about 3 years and I think 8-16gb of Ram will be the norm.
The only reason it will take that long is that there are so few people on 64-Bit OSes right now to justify creating enough bloatware to make it needed for that much memory.
Even most of the Vista copies now shipping are most likely 32-bit.
I don't have any figures, but that is what I would guess.
If nothing else just to maintain 16-bit app support which is lost in the 64-bit OS and limit complaints from folks with little IT knowledge who are buying these sytems.