Yep, the Unions will lose.
The democrats can only sue in court.
But all Walker has to do is call a democrat senator as a witness, and when he's on the stand convene the senate right there in the court! The GOP senators will be conveniently in the stands. Wala, the original bill is passed!
So now there will two versions of the bill passed. No mater what, one will be in effect and its perfectly legal.