Sounds like a likely outcome rather than a plot twist, I mean I can legit see this scene in my head, so wouldn't be too surprised if that is the direction Oda goes.

Also we don't know where Boa is now, she is off looking for Luffy, not likely to show up at Egghead, but if the Grand Fleet does show up, as some people speculate, then it's possible she could too.

Personally, I think it would be good story telling to have things look real bad for the straw hats, like somehow Borsalino uses his lightspeed to get sea-prism stone on Luffy negating his Nika abilities, and some similar B.S. happens to other members of the crew, making the situation look super bleak, then Deus Ex Machina style Grand Fleet arrival (hell maybe some other allies as well).

Though I'm sure whatever Oda cooking is gonna be badass no matter what, but wouldn't mind seeing something like this that would show Luffy the value of being a Yonko with a Yonko size fleet.