Kasich could win a congressional district or two, and thus still rack up a few delegates. As long as he does that, he arguably keeps some degree of viability until April 19. And, who knows how much Trump could implode until then.
Cruz and Trump are in a virtual tie there.
And, after Wisconsin, there's nothing in the hopper until the April 19 New York et al. So, why drop out just because of one primary? Beyond the delegates Kasich has, Rubio still has his.
Meanwhile, the Democratic side is a big test for Bernie Sanders. Open primary in a state that's largely white outside metro Milwaukee. On the other hand, Ohio and Missouri, both somewhat similar and both open primaries, were both won by Clinton. But, not totally similar ... both those states have twice the African-American population percentages as Wisconsin. Of course, Michigan of his narrow win had an even slightly higher black population.
Polling remains split in the state.