Bad Idea Sprint
So, right now Sprint has very small advantages over the bigger carriers. One of those being price, and one being true unlimited data. Raising the price (on an already hiked price) and/or dropping true unlimited screams "run to the competition" to me.
Sprint is one of the slowest to adopt new stellar phones (about 1-2 a year, while Verizon is grabbing about 4-5). I had my first taste of 4G and hit a download speed of 1.8 Mbps with 0.13 Mbps up; I switched to 3G and got 1.5 Mbps down and 0.38 Mbps up. So, 83% down and 300% up on 3G makes me think 4G is not living up to the expectations, plus the battery drain is idiotic, and I'm being charged for it when I don't get it anywhere closer than 3 hours away. So 4G isn't Sprint's killer feature (and other carriers are already gearing up to catch and surpass Sprint on this). Sprint's coverage isn't as good as the larger two either.
So really, Sprint isn't in the position to be jeopardizing the tiny thing keeping some of us loyal customers around. If they marginalize the differences and homogenize the market (collusion / monopoly-like much?), why pick #3 when you can easily go #1 or #2 for little to no disadvantage.
This tiered/metered/capped Internet stuff is a bunch of garbage and all the carriers/ISPs better figure it out fast. We don't want to pay more for less.