You might be right with your prediction of the importation of massive numbers of paid anti-Trump protestors to Indiana Trump gatherings... but I suspect the wind is out of the sails of the anti-Trumpers.
I tend to agree. Flipping between CNN and FoxNews last night, there seemed to be a resignation to the fact that Trump is now the presumptive nominee and the window for boxing him out is now closed. Character assassination won't work - the people know who Trump is. Disrupting rallies by sending protesters has proven to be ineffective, in fact, Trump feeds on that and seemed genuinely disappointed there were no protesters at a recent rally. Party parlor tricks such as "wrangling delegates" and making the process confusing for voters also seems to have badly backfired.
I suppose it's theoretically possible that Trump stumbles in Indiana and Cruz pulls out a strong victory like he did in Wisconsin. But I just don't see it. Trump has all the momentum and his rally there tonight with Bobby Knight looks to be a barn burner.