The idea of Massa for Mercedes would open up all kinds of options for next year in the Driver's Market. The hole at Ferrari may well be filled by Kubica should he have effected a full recovery - regardless of his feelings for Renault could he pass up an opportunity to pit himself against Nadgers in equal machinery (and Prancing Horse to boot).
The only other viable options for Ferrari would have to be Nico/Vettel or Webbo/Button. I can't see Button going anywhere given his expressed desire to end his career at McLaren (prior to contract negotiations) and I don't think Webbo could take it should he compete with Nadgers and be found wanting (given Vettel's current dominance at RBR).
The question is then whether they pay an exorbitent fee for Seb in order to create a super team of Nadgers and Seb or whether they go with Nico to give him the opportunity to push Nadgers: Nico - son of Keke - definitely good for sponsorship!
The who fills the other vacant seat at Mercedes? Webbo would feel that he could compete with Massa in equal machinery - Hamilton (while unlikely to leave McLaren given his current statements) has expressed (an unexpressed) desire to go elsewhere by way of his early criticism of the team but Mercedes might not be big enough for him, Red Bull would not take him (or would they?) after he called them fly-by-nights, and Ferrari couldn't have him (with Nadgers in the team) - basically he's ****ed from a height with regard to competitive teams - I'd day his management team have finaly realised this and hence the resulting soothing noises currently audible in the Hamilton camp.
So we have:
Ferrari: Nadgers & Nico/Kubica
RBR: Vettel & A.N.Other
McLaren: Lewis & Button
Mercedes: Massa & Webbo
Renault: Nico/Kubica & Heidfeld/Petrov
preview To be finished later