They may still implement their own congestion control
It's naive to singularly attribute the move to UDP to an anti-social desire to eliminate congestion control.
There are a bunch of reasons to move bittorrent from TCP to UDP, the most significant of which is that automatic NAT traversal can be more easily performed with UDP.
When they move to UDP they will need to re-implement some of the things you get for free in TCP, such as reliability. There is no reason to assume that they will not also implement their own congestion control. It would be shortsighted of them not to - the most commonly congested link is the one between the home and the ISP, so the first person to suffer would be the bittorrent user.
Biting the hand that feeds IT
