It's not confirmed by Sony just yet, but Videogaming247 says it has it on "good authority" that the upcoming version 2.40 firmware update for the PS3 will at long last bring with it in-game XMB, as well as the slightly less-anticipated trophy support. If those sources are to be believed, the update will be dropping sometime in June, with some speculation further pointing to a release in advance of Metal Gear Solid 4's June 12th launch. There's apparently still some testing to be done to ensure that the in-game XMB will work with all titles, however, and it seems like features like trophies and user-music via XMB will only be supported in games created with the new developers tools that have apparently already been released in advance of the firmware update.
[Via PS3 Fanboy
, thanks John]