"We think this title, never having been released on any handheld platform, has the potential to sell several million units at launch, at a $49.99 price point." (Note about the novelty of the release: there is Guitar Hero III Mobile, but that doesn't count.)
He also said that large retailers like Best Buy, Target and Wal-Mart will feature the handheld title prominently in their stores, contributing to the sales. That makes the most sense to us: a Guitar Hero game in a smaller box must be a very attractive item for retailers.
Gallery: Guitar Hero: On Tour