From an AvWeb/Oshkosh article on the GAP engine (a two-stroke diesel that Continental is developing):
If the test-cell endurance runs and the Skymaster flight trials go well, then by AirVenture 2001 we may see GAP engines flying in three more demonstrator aircraft: a Cirrus SR20, a Piper Seneca IV, and maybe even a six-cylinder 300-HP version in a Lancair Columbia 300.
But: …it is still a long way from certification – perhaps three years away.