Nah, I think Costa will go to Chelsea. Mourinho loves a cunt, especially when they're big, strong and score bucketfuls. There's also the not-inconsequential Mendes link. Falcao is older than he should be and won't bring the physicality either. His aerial game won't be as pronounced either in England where defenders tend to be better here than on the continent.
Too many palms will have to be greased to get Costa which is why we won't do it. What you say makes sense that Lukaku might be used as a sweetener for a Diego Costa deal while Eto'o/Ba are kept around. Some stupid Russian club will probably give Chelsea way more money than Torres is worth, so he might leave too.