Rather than have it die in a proprietary silo, open it up like Netscape did with its codebase. Once it hits the scene I really think it would capture people's imaginations. Plus, it ain't Java (tm)
I don't think that such an arrangement is in HP's character; however, letting the investment die seems foolish in any case.
It's all about developers and the ecosystem. Ballmer was right about this. Apple nailed it. Facebook nailed it in the past. Everyone who attracted developers grew and got a lot of publicity and new stuff they never dreamed about.
HP could lead the development of WebOS and that would be a great opportunity for them. Even if it costs them $10mil a year to maintain, it would give them OPPORTUNITIES that right now they are throwing away. Open source tends to do that.