I dont see how you could guarantee as much Linux development if both are available at boot. Obviously there will be a split of resources or people saying that if you dont have a certain kind of software on Pandora you can anyway use Android. Its for the same reason some people think WINE is doing a disservice to pure Linux gaming on desktops and I think they have a point.
Are you talking about development of the OS or development of software? I thought we were talking about the former. Android availability is going to be a given either way, it's even available on Pandora now. I don't think making Android a little more accessible will make people lose interest in developing for the Pandora OS.
The big problem with that argument against WINE is you can't actually provide very solid evidence to support it. You could look at game availability on Linux vs WINE maturity over the years but I don't think you'd draw very much from that...