For years, people have been putting four-stroke dirt bike engines (mostly, Honda XR motors) in 80cc motocross chassis. Last year, Yamaha came out with its hugely successful TT-R125, a four-stroke in an 80-sized chassis (without the high grade suspension of a racing 80).
Along with rumors that Yamaha is developing a four-stroke for its 80cc mx chassis, are rumors of at least one new small four-stroke machine from Honda — probably an XR, rather than a CR.
Honda has long dominated the beginner dirt bike market with its smaller XRs. Yamaha has clearly taken market share from Honda with its TT-R125. Expect Honda to fight back, soon, and expect several new models (from several manufacturers) in the beginner dirt bike market.