There are lots of manufacturers with factory 300cc two stroke... There are more with 300s then without, Beta, Gas Gas, TM, Fantic, KTM, Husqvarna (bmw and KTM version) and I am sure there are some i'm forgetting. The 300 is an outstanding motor, but I feel that until there is a series letting 300cc+ two strokes race in the 450f class the big 4 have no reason for them, being there MX/SX based. IF the big 4 (honda, Kawasaki, Yamaha and Zuki cared about us off-road guys we would have at least one other off-road ready bike to pick from than the crf450x and wr450... Yes the yz250fx an 250x are making there way into the world but still can not compare to the options you get for European off-road bikes.
Not trying to be a KTM or European fan boy but Japan no longer makes a bike that suits what I need. Except the super tenere, I really want one of those