Not that I have any actual information, but I really doubt we'll see Nikon or Canon joining 4/3s. With Samsung showing that a similar sized product can be released in APS size it makes sense for them to compete in that market with their existing lenses to add to any new system they have. But who knows.
Now Fuji is a different story. There were actually 5 companies that initially signed on to the 4/3 standards. Panasonic and Olympus of course, Sanyo (which is now Panasonic), Sigma (presumably for lenses but who knows) as well as Kodak and Fuji. So it isn't unreasonable to think Fuji might come out with something since they already belong and clearly had that intent some years ago. But other than feeding the fires of speculation and wishful thinking, I have no actual new information about whether that will actually happen. But dreams are nice.