Since you have the experience, you are now ready for the Turrrrboooo Busssaaaaa!
Seriously, though, a big sport touring bike would be fun; ZX-14, Hyabusa, FJ1300. I love seeing older guys riding something that would scare the crap out of me. I remember the first time I saw a 950 Adventure. It was a guy in his mid 70's, and he was telling a crowd about a Can-Am Spider that everyone assumed was his. Then his little old lady wife drove away on it, as he through his leg over the tallest dirt bike I had ever seen up to that point, and rode away. There were at least 5 riders picking their jaws up off the ground.
...and 58 is only 17 years ahead of me, so don't act like yer old.