The carriers don't really give a $!?$&@ about device upgrades. They'd be happy to quit subsidizing those smartphones. Subsidies back in the day for dumb phones were only around $150-$200. Smartphone subsidies are normally $400+ and ATT at least is really looking to discourage subsidized contract price purchases. Carriers lose money on subsidies, carriers make money on service.
It's no secret that subsidies only serve to artificially inflate the true price of phones. With these subsidies gone, I think the full price of phones will come down a bit, as they'd no longer be artificially pumped up.
I like ATT's options. Pay $800 at once for a new phone, it's unlocked on day 1, and keep my low rate. Or, I can pay nothing today, add $30 or so to my monthly bill for the next 24 months, and have my phone unlocked after the balance is paid off, or if I really want to, pay $300 out of pocket now, get a locked phone, pay $25 extra each month for 24 months, and be held hostage by an early termination fee. First two options are virtually the same, one pays the $800 up front, second locks the phone and finances the $800 over two years interest free, and unlocks afterwards.