"We will be updating the TOS to require you to check t.co and register the click." Damn. Looks like URL shorteners are here to stay, permanently, and twitter is crowding out all existing link shorteners.
While they'll "wrap" other shortening services, what's the point now? People won't use them and they'll fall by the wayside. Not really a bad thing in my opinion (people use them now when they don't even need to) but still a bit of a smack in the face to services that essentially helped Twitter in their early days.