Given that Google's charging for Drive and not G+, it kind of seems like the other way around.

There's always a risk a company will either shut down a business (Symbian, Wave, MySpace, Delicious), or go out of business (Chumby), or get bought and have their business shutdown (Sidekick, Drop.io). I don't think you can really know the future enough to make product choices based on the chance that will happen.