[Optimus Clyde]

First, let me say that no toy comany would conceive of a toy line unless it can work in the "long term" of the market it inhabits, say 6 months to 2 years...long enough for a Christmas or two...or a summer movie tie-in. If, however, we're talking about "long term" as it applies to the institution of the "crossover" in general, well, as a lifelong geek, I love the idea of crossovers, and they've been around for a long time in geek culture, though mostly in comics. Some of Hasbro's most popular lines have already crossed over in the pages of Marvel comics. With the right timing and support (comics, TV, web), some toy companies could use a crossover to bolster interest in any of their lines.

Transformers Crossovers are cool, but as they are, they're nothing more than a novelty. They're not truly a "crossover" because, in the case of both the Star Wars and Marvel lines, none of the Transformers characters are present.

Otherwise, again thinking along comic-book lines, properties that Hasbro owns outright could be thought of as a "universe" of their own. Given that, anything is possible. GI Joe, Transformers, M.A.S.K., or any other property could be mixed and matched to suit whatever purpose they wish. The same may be be possible for Mattel, I suppose. (I don't know enough about their lines to say if it makes any sense. He-Man / Hot Wheels? :P )

I think the question, though, is to what extent any company would want to take the "crossover". If Hasbro creates more crossover lines, will they just be more novelties like Star Wars and Marvel Crossovers? Will they just be gimmicks like the licensed Mr. Potato Head and Mighty Muggs toys? Or will they flesh out a passable scenario complete with fully realized storylines where characters from each line interact? That's what I want to see, but I don't think it's very likely. At least for now...