Tony Hawk's Pro Skater HD remakes the first two games and mashes them into one. But as mentioned previously, there's more to come: the third and arguably last great game in the series will be making it in there as well via DLC.
Now, where the vanilla game will run you $15, the remade content from THPS3 will run you a fair $5. To put it another way, it's ~$6 per game -- not what I'd really expect of Activision, so kudos.
The DLC will contain new levels (including Airport), and more pros, and will launch between 30 and 45 days after the base game (July 18), though beyond that I don't know much.