Heh, I mean shit, I just picked up an XBox One like 3 days ago. PC gamer ordinarily, I just know that sort of non-changing hardware is one of console gamings last big draws in many ways.
Look at the difference between iphone and ipad - the key one is that iphones are bought largely on contract, so there is an impetus of sorts comeplling year on year replacements. By comparison, the iPad doesn't have any sort of impetus, relying purely on hardware improvement hype and it falls comparatively flat in comparison. Take contracts out of the equation and I doubt you would see phones replaced so frequently.
I'm probably a poor example as I buy an off-contract phone just about every year (it actually ends up being cheaper with prepaid plans and reselling the old model).
I think the console manufacturers could do something similar (not contracts but incentive updates through guaranteed trade in value.) Buy an Xbox or PS and pay $70 a year for PSN/XBL and guarantee 75% trade in value at 1 year 50% at 2 years.
I think enough people would would think "Gee I can get upgraded graphics for only $150" and MS and Sony could resell the refurbished units as a lowcost entry into their ecosystem.
Yes, I realize it will never happen but I think it is an interesting idea.