https://blogs.microsoft.com/on-the-issu ... verywhere/
This is a smart decision by Microsoft to increase the value of their subscription service (and of course basically encourage people more in the direction of actually keeping the subscription service and being a lifetime member essentially, although you'll never actually own any of these games).We are expanding choice in two ways: through the creation of Game Pass, which gives players a subscription option; and by bringing more games to mobile platforms, including through our cloud game streaming technology. Subscription services like Game Pass make gaming more affordable and help players from all over the world find their next favorite game. Game Pass empowers developers to bring more games to more players, not fewer. We intend to make Activision Blizzard’s much-loved library of games – including Overwatch, Diablo and Call of Duty – available in Game Pass and to grow those gaming communities. By delivering even more value to players, we hope to continue growing Game Pass, extending its appeal to mobile phones and any connected device.
But besides that, it would be interesting to see how everything plays out given that this would mean D2R basically becomes a free game (through the service), D4 as well, and it would be very interesting if WoW also gets included. This means it's more affordable to just pay for game pass than paying a $15 subscription for just WoW lol.