Today, via a Capcom Unity post, Capcom announced that Mega Man X4 & X5 will be joining the library of PSone Classics on PSN. These titles will be playable on either the PS3 or Vita consoles. The games will be a nice addition for fans of the series looking to relive some classic moments. And I bet they will play great on go via the Vita as well.
X4 will release on September 2nd and X5 will release the following week. If you still want more in the series, you might want to check out Mega Man 1-4 in the PSone imports, Mega Man Maverick Hunter on PSP/Vita or Mega Man 9 and 10 on the PS3, which are all available on PSN right now.