Ill wait until it officially releases on Battle.net. I would hate having my Blizzard games all over the place. Besides I don't use GoG. Good for those who are craving it.
If Im not mistaken, Diablo 1 will never come to battle.net(at least as it is now), due to battle net not handling the code/launcher/something along those lines well.That is the reason it went to GOG because they speciallise in old games.