I liked the idea of the prestige system but I can understand peoples doubts. It would of affected the economy and left little room for future content as people would be content grinding out the old content.
Instead of prestige I would suggest raising the lvl cap of all skills to 120, my reasons for this are:
1:
It allows people to train past 99 and feel a sense of accomplishment with every milestone.
2:
It allows for much new content to be added to the game ( I wouldn't expect the content to be released straight away, but in the future).
3:
New capes. There was some fan art on Deviant art with some new look skill capes that would look awesome for 120.
Also I would suggest making better use of the seasonal high scores, monthly skilling competitions would be nice, with title rewards and a place on a permanent monthly high-score table that shows the winners for each month of a year. This would provide fresh competition every month.