Since the PSVita was announced Sony have said it will be backwards compatible, The PSvita has no UMD slot so how can this be? The games according to Dengeki Playstation can be downloaded to the PSVita but at a price.
Sony Computer Entertainment Japan have said that they will be considering a spacial offer where UMD owners can download the games at a spacial price. No information on this offer has been stated for the UK/Europe or America yet.
The PSVita launches in Japan on December 17th. We still await a UK/European and American release date.