Microsoft pointed aanswering questions about the transition.
As for purchasing Microsoft Points cards: "You’ll use local currency or an Xbox Gift Card (denominated in your local currency), in addition to other current payment methods available in your region, to purchase your favorite content on your Xbox 360. The next time you initiate a purchase or redeem a Microsoft Points card or code on your console with your Microsoft account, we’ll add to your account an amount of currency equal to or greater than the Marketplace value of your Microsoft Points, and your Microsoft Points will be retired. The currency we add to your account at the time of the transition will expire on June 1, 2015. However, the currency you purchase and add to your account after the transition will not expire."
Let us know if you found your MSP turned into cash.