Ballroom gives me the opportunity to perform, which I will miss, even though I often thought that the expectations of competitive ballroom were both artistically and socially restrictive (especially at higher levels). Piano doesn't offer many performance opportunities, especially for adults, unless you're really good. Because there are lots of "good" people out there. I haven't performed a piece publicly since Rhapsody in Blue for my senior recital (and I definitely can't play that one anymore), and I don't see many opportunities to play for others in the future. But the times I enjoyed piano most were when I was just playing for myself, anyway, so maybe performance doesn't matter so much after all.
I'd love to learn more jazz and improvisation, but nothing will ever compare to my favorite Romantic and Impressionistic piano pieces. Improv is fun and playful and unpredictable and all, but most people can't get the emotional complexity and intensity in a piece unless they rehearse it and really explore all of its intricacies. Even jazz players often have their pieces more or less fixed to be able to start drawing out the interesting details. (zestyping may disagree -- I kept meaning to write my own rebuttal to his assertion that classical music is boring and rote, but never found the time, as usual. But my playing certainly didn't feel "dull and uptight." And most of the improv I've heard is emotionally dead in comparison to my favorite works of the great Romantic and Impressionistic composers, in my opinion.)
I'll have to invest in a weighted keyboard (or even a real piano, though that's unlikely) at some point if I really do want to do this -- my touch-sensitive keyboard serves me very well, but it's just not the same. But I really do need some music back in my life, and piano used to fill that void so well. I hope it can again.