Welcome in here Bigcountry29340! Congrats on your first post in the forum
I'm assuming there's only one crossover per Season? So if they're going to do one this year, I'll say crossing over with "Scorpion" seems the most likely. Lucas said he'd love the shows to cross over and he has already worked with Robert Patrick years ago and they met up this summer in Monaco and had a good time.
The biggest "problem" is Scorpion being filmed in LA with MacGyver being filmed in Atlanta, but this distance should be easier and cheaper to manage than last year's crossover with H50.
Also, Scorpion's ratings have been falling quite a bit, so that might give them a boost.