Thanks for posting this. Great read.
I find it hard to believe that Hamilton would leave for either Ferrari or Red Bull. The former simply haven't shown consistent form in the past few years, and have a more traditional #1 - #2 driver strategy. The latter is effectively "Vettel's team", and it would block Red Bull from promoting any of their own very capable young drivers (Vergne, Ricciardo, etc.).
However, Mercedes is a distinct possibility. Nico Rosberg is not an assertive, domineering driver like Vettel or Alonso, so he would be a good match for Hamilton. The only question mark is Mercedes' long term viability (will they stay in the sport or not?).