The solution here is for publishers to give away the client, and simply charge a subscription.

Keypoint:

  > would require a digital game operator to communicate specified information to purchasers and prospective purchasers of a digital game 60 days before the operator ceases to provide services necessary for the ordinary use of the game, and, beginning on the date an operator ceases to provide services necessary for the ordinary use of the game, require the operator to provide the purchaser with an alternate version of, a patch or update to, or a refund for, the game,

"or a refund for the the game".

"Here's your $0 back, thanks for playing!"

That makes it a bit tricky for games like WoW that charge for expansions, as well as subscription. But I'm sure MS can figure something out.