PS3 can stream single files and it can play m2ts. But I don’t believe the PS3 can stream the entire blu-ray structure. That means you will not be able to retain the menu, pop up menu etc. Also the PS3 might not be able to play some video or audio codecs in an m2ts (you will need to test it).
Also if the main movie is across several m2ts files it’s not going to be good for you. So I guess for some movies we are still stuck with the discs.