About a month ago at Gamescom, Sony announced its PlayStation Plus service would arrive on the PS Vita and that the storage limit for the cloud would be increased. While we're still waiting on a date for PS Plus on PS Vita, the PlayStation Blog says the cloud storage expansion is coming with the next PS3 firmware update, version 4.25.
The cloud storage cap for saved game data currently has a ceiling of 150MB. Sony says v4.25 will be available "soon," though no specifics beyond that have been given. We've contacted Sony to try and get a better idea of when we should expect the firmware update.