Oi Marao,
Tudo bem? I have no idea about university, but I did switch from classical guitar to piano at age 38. I loved the guitar, but here's why I love the piano more:
1. Much bigger repertoire - the guitar has a good Baroque repertoire of transcriptions, and some good late Romantic and modern Spanish and Latin American music, but there really isn't much in the heart of the Classical period. Fernando Sor and Mauro Giuliani are pretty much lightweights compared to Mozart, Haydn, Beethoven, and Schubert. There's so much more great music for the piano.
2. The guitar has a nice, intimate sound, but it's really fun to make a lot of noise on the piano. You have such a wider dynamic range available.
3. Native born pianists may differ, but I think piano is much easier to play than guitar. Only one finger to play each note, and the notes are all right in front of you in a logical pattern. It's a heck of a lot easier to play even a moderately difficult fugue from Well Tempered Clavier than to play even the easiest fugue from the Bach violin sonatas (e.g. the G minor). Eliot Fisk astounds people by playing fast Scarlatti sonatas on the guitar, and they sound really tough and virtuosic, but the same sonatas are pretty straightforward on the keyboard.
I don't doubt that if you work intelligently and with a good teacher you can get to a pretty satisfactory technical level, even starting in your forties. After 15+ years I'm playing things like the C minor, D minor, Ab major, and Gmajor P&F from WTC 1, Beethoven Sonata Op. 10 no.1, most of the Schubert Impromptus, 4-5 of the Brahms pieces in Op 177 & 118, and my teacher just pushed me to start the Revolutionary Etude and the Black Keys Etude. I've been averaging 2-3 hours/day over most of the past 5 years, less when I was starting. I wasted a bunch of time at the beginning for lack of a good teacher. It's all a hobby, though, and just for fun; I've no delusions of making a career.
P.S. I'm married to a Brazilian and would have written in Portuguese, except that the last time I did that the moderator slapped me for not writing in English.
Best regards,
Bill