A new update for the PS3 system software (v4.25) will come with an increased amount of cloud storage for game saves for PlayStation Plus members.
Currently, the PS3 offers cloud storage for online game saves of just 150MB. It was announced at Gamescom that the storage limit would increase to 1GB for PlayStation Plus members, and the PlayStation blog has revealed that the increase will be coming with the update to v4.25 of the firmware.
PlayStation Plus members will be able to take advantage of the extra space as soon as the system updates, and of course all existing saves will still be there.
The blog post doesn't mention when the update will be available, but looking at the comments, Sony rep Morgan Haro has said, "this should be available later tonight."