I think it's a question of whether or not the public will want to see it. I think they will, just coasting on the hype as a result from the trilogy. However, in my opinion (and I know it would never have worked this way), it would have been better if we'd seen The Hobbit first. That way, it would be a step UP (as far as plot, quality, development, etc.) instead of what it might be now -- a step down. Of course, being that a good deal of time passes in Mirkwood, I suppose they could devote some time to that hunky hottie, Orlando Bloom!
I also think that, if they are unable to get Ian Holm, then they should abandon the idea altogether. He isn't very young anyway, (yes I know that age thing at the end of RotK was just makeup, I'm talking in general
) so I question whether or not he'll be able to carry off being the main character, and the strenous tasks involved. Although I once heard that Elijah Wood said he'd be charmed to play in The Hobbit. I wonder if anyone has told the dear fellow that Frodo isn't IN the Hobbit?