There's a discussion on this going on over at Google's product forums [1]. Tons of people are in the same boat. These are some of the most devoted users of Google's products, yet are continually left frustrated and left out of new products for seemingly no apparent reason.
And no - migrating to a regular @gmail.com address isn't really feasible. I'd have to manually export all of my playlists, library, favorites from Play Music and countless other products.
[1] https://productforums.google.com/forum/#!msg/play/86WVa8b_3i...
Project Fi is another service I'd love to sign up for, but my Google Voice number I've been using for years is associated with my Apps account, and I'm not about to start another number and start switching between Google accounts all the time just to use it.