Hamilton's definitely not planning on looking for any new drives any time soon, but he may fall into the same trap Senna did. Senna became the most expensive driver on the grid as much because of his marketability as a sporting icon as for his talent in the car, and Hamilton looks like he will be the same, but towards the end of his time at McLaren the amount spent on Senna's salary was money diverted away from developing the car, so his car and career suffered as a consequence. Hamilton must watch this.
But seriously, after all that's gone on in the last two years, I can't ever see Hamilton driving for Ferrari.
To be honest, I never really saw Senna's salary at McLaren as a big issue. To be honest, at the time, McLaren were only team who afford to pay that kind of money and still be competitive. What messed things up for McLaren was Honda deciding to leave Formula One. The beginnings of things going wrong were in 1991, when Honda's engine wasn't as good as their usual standard. In 1992, - disgracefully - they didn't give a toss and a had the cheek to provide McLaren with a load of rubbish, which was a real shame, for the MP4/7 chassis was pretty good. Thereafter, the engineers weren't able to design the car properly, for they had inadequate information about the specifications of the engine, which, again, was really a pity, for some of the chassis were great. The MP4/8 was a brilliant piece of engineering from McLaren. If it had a decent engine, it would have won the title without doubt.
Let's say McLaren do have a dip in form in the coming years. Who's to say Hamilton will go to Ferrari anyway? Ferrari are not eternally successful. There are years they produced mediocre cars, but won titles because everybody else was so average. Ross Brawn himself said that. McLaren, for instance, had all kinds of political problems going on from 2000-2005 which affected the team's performance. There are several teams now who see themselves capable of challenging for races and titles. If McLaren aren't up to standard, Hamilton will go to the team that is. Irvine is talking complete rubbish.

Ayrton Senna: WDC 1988,
1989, 1990, 1991
McLaren: WCC 1974, 1984, 1985, 1988, 1989, 1990, 1991, 1998,
1999, 2007McLaren: WDC 1974, 1976, 1984, 1985, 1986, 1988, 1989, 1990, 1991, 1998, 1999, 2008