Mark Renshaw is a brilliant bike rider and a brilliant guy, but neither he nor Matty Goss are sprinters, not proper sprinters in the mould of a Cav, Cipo or even Petacchi and they all would realise that they are in a lucky position with Cav, I mean look at his last two teammates that left to "make it on their own" Messrs Greipel and Ciolek. Both are happy to take whatever crumbs are left under Cavs table.
Mark recognises he is way better off as Cavs right hand guy, Bernie Eisel is the same, wherever Cav goes they will go. Matt Goss is a different kettle of fish altogether - he is after all only 24 and has already won M-SR I think it more likely that he would be the heir to Boonen's crown (or Fab C's) in the Spring Classics, he is big, strong, fast as hell and can ride like a man possessed.
Cav IMHO would not be well served by going to Sky in any way other than financially. He would be joining a team built around GC success, it just wouldn't suit him NOT being the complete centre of the team. Wiggins would leave within a year regardless of what he says now.
But it will be interesting to see what happens. I spent half an hour up Alpe d'Huez last week while waiting for the final km kite to be blown up with Mick Rogers, he was keeping his cards pretty close to his chest, but reading between the lines, Cav will be in black and white next year (with a thin blue line)