If you count the Crop factor, sure why not? afterall, 300mm FOV isn't that tele.
Ah...so crop factor applied to focal length, not just FoV? You must be in some weird, Star Trek-ian mirrored universe where the normal laws of optical physics don't apply. Say "Hi" to evil Mr. Spock while you're there...
Just imagine a world where 35mm didn't exist and only M4/3 did. Then we'd all be saying how 150mm is very tele and unless I'm mistaken, 150mm on m4/3 is pretty tele.
Context is important, but since everyone shoots 35mm, I just put it in those terms. Eh Neuro?
Funny how everyone is happy to convert the focal length to 35mm terms, but not the aperture... This would give you the equivalent of f/4 in 35mm terms. Useful, but doesn't sound as good as the "300mm f/2" you quoted in your original post. On top of that, as others have pointed out, the 150mm f/2 is "regular" 4/3rds and so on micro-4/3rds bodies, will focus even slower than the Canon M
As CanNotYet points out, there are two native micro 4/3rds lenses that get to 300mm available; not only are these slow, optically they aren't that great at the long end.
None of the mirrorless systems yet have compelling long lens options, which means that they lose appeal as DSLR replacements (as opposed to supplements) unless you can live with lenses below ~200mm (in 35mm equivalence