The Hardy Heron is the next release

Hardy Alpha 3 was 10/01/08
Hardy Alpha 4 should be 31/01/08
Hardy 'Feature Freeze' (final release features) should be 14/02/08
Hardy Alpha 5 should be 21/02/08
Hardy Alpha 6 should be 03/03/08
8.04 Beta should be 13/03/08
8.04 RC (release candidate) due 17/04/08
Ubuntu 8.04 Hardy Heron due 24/04/08

They are the dates I have seen, but as noted, they are subject to
change depending on what the testing throws up!

Hope that clears things up for you.