Developer Robomodo is working on the development of the new Tony Hawk HD. It will take the best of the first two games in the franchise and bring them back with stunning HD visuals and improved game play, while keeping everything that made the original Tony Hawk titles so good.
If sales of Tony Hawk HD go well, then what Robomodo would like to do is be able to release levels from Tony Hawk Pro Skater 3 and 4 for sale as downloadable content add-ons for the game. The new Tony Hawk HD features an all new HD engine to power the new enhanced version of the levels from the first and second Tony Hawk games.
Activision, Robomodo, and Tony Hawk himself all seem to be very positive about the new HD version of the game. In addition, they are all very excited about doing a core franchise title like this as a downloadable game. Offering a number of DLC add-ons is possible if the game sells, but it will need to sell well before we see Activision skinning more money into it.