That is exactly what happened to me. I never had really regular tastes for music and listened to the occasional piano music but old American folk aka mountain music and bluegrass were my thing. I was really into that style, i even bought/learned the banjo and joined a band. I still play in the band and enjoy it but i listen to almost exclusively classical now. Other music just sortove seems boring.

My latest purchases though are:
Mahler's 9th
Bruckner's 5th and 9th
Barber's Agnus Dei

I tunes is currently crippling my bank account!