Has there been any indication about Haas and how much money the team will have behind them. Are they going to Toyota it and throw silly money at it, or the next Caterham.
If he felt like there was one last challenge, building a team up from nothing would certainly fit the bill of extreme challenge. Ferrari is one of the toughest jobs because of the pressure and expectations. Ultimately it could come down to money, or loyalty. Have no idea what drives him, Red Bull might be able to offer him 10mil a year but refuse to give him more than 2mil while another team might offer him 10mil, or team principle, who knows.
He might want to leave, he might not, certainly be more interesting as a whole for the sport if he did. If he went to Ferrari/Haas/Mclaren, would RBR fall apart, could he create some magic again, would we get an old favourite come back to the front of the pack.
Merc are making a brilliant car though and have put together a team to rival RBR for sure. Great engine....maybe, though the RBR did fine coming through the pack against other Merc engines. But 50 second gap at a less engine limited race, where everyone expected RBR to close the gap at a track that was more aero limited... speaks exceptionally highly of the Merc car aerodynamically.
Though I think people called the engine issue incorrectly. Less max speed, sure, but more braking, more corners, more harvesting of power. Back to a really really efficient harvesting and application of that electrical power for constantly acceleration and keeping the turbo spun up could potentially make where I think the Merc excels the most, efficiency/ers systems, very very important at these tracks.