I think by music store the rumor surely means a record shop since we have an instrument shop in Assembly Square already. Could be really awesome to see printed tiles with brick versions of famous albums. A record shop is my number 2 most wanted modular after a post office though so maybe it's just wishful thinking. I love the idea of a strip mall type building as well.
Easter Eggs seem like bunk to me, but the old woman sitting on bench in front of the Museum does have a letter next to her, so maybe we'll finally get our Post Office.