A large part of their profit margin comes from making only very few models that share commonality in parts. Nobody is screaming for an optical drive either, so I suspect that the old unibody laptops will only be kept around for 1-2 years until demand decreases.
There's bound to be other companies that will cater to that market, but they won't be able to ship OSX on their laptops.
http://blog.macsales.com/9102-secret-firmware-lets-late-08-m...
Looks like this won't fly in the Early 2008 MBP, but you might be able to get 6GB in there (note "Standard RAM"):
http://www.everymac.com/systems/apple/macbook_pro/specs/macb...
With the MBPs sold in 2008, all of them support 6GB even though Apple claims only 4GB. Go ahead and try it. If it doesn't work I'll pay for your RAM upgrade.
So now, I have the option of maxing out the hardware _hoping_ that it will last me many years. That's part of buying into a closed platform _and_ belonging to a niche of consumers.