I had a student at one of my workshops who was 93 years old. She played piano already but wanted to learn chords just to learn something new. Many of my students have been in their 70s and older, so I haven't figured out exactly when you''re too old.
Some people have a natural inclination to learn piano and, even at an older age, will learn faster than a younger student with less inclination. Ive also seen students who struggled to learn the coordination and other skills necessary to play but were absolutely determined to do it--and they did.
But mostly, I believe, it's your attitude. If you want to learn, then decide you're going to do it and then do it. If you're just curious about what it would be like to play the piano, you may be disappointed to find that it takes commitment and dedication to play even rudimentary piano.