The 3DS might limp its way to 70 million, and that system's "hook" did it no favors. So 100 million for a system with a hook that people are obviously intrigued by seems reasonable. Once the 3DS wraps, Nintendo can use all the weapons in their arsenal, up to and including at least one main series Pokemon game exclusive to the Switch. They should get a couple good exclusives from Japanese third parties like Monster Hunter and Yokai Watch. Hopefully they get at least one new franchise to catch fire to really put them over the top.
There are many obvious pitfalls that could stop them but I'm sure they've already been said in the first seven pages here. Still I'm relatively optimistic from this start.