Max Raid Battle should be against Gigantamax Pokemon (which only appear in Galar).Go will definitely be involved even if he loses badly. And no, if this were a Max Raid it wouldn't just be called a Raid, which is a Go term.
And the speculation about old characters needs to stop if there is no real hint.
In Episode 2, the term Raid Battle appear when a group of trainers battle against Lugia. So, it's pretty likely this term will still be used in this episode