The MMA-boxing crossover fights are all the rage these days, after Conor-Mayweather RAKED IN cash ... and now everybody wants in on the action.

Nate Diaz called out Canelo after Alvarez signed his blockbuster $365 MILLION dollars ... and Tyron Woodley told us he's down to step in the boxing ring too.

So, will a Gennady Golovkin vs. MMA star fight actually happen? Maybe, maybe not.

We will say this ... Dana White says he met with Floyd Mayweather's camp about a possible MMA fight with Khabib -- which is how things got cooking with Conor McGregor.

The issue ... Floyd told us he would only take a boxing match. Dana is adamant it can only happen in the Octagon.