Will retail and classic eventually be merged?

Only if we the consumer ever stop paying and playing. Blizz keeps reskining old games that we loved and reselling them to us relying on the nostalgia. They did it with Diablo II, they did it with Warcraft III, they did it with WoW… they’ll continue to do it since it’s a recognized IP with low risk and less effort then coming up with something brand new.