If you look at the sales for SOTC and ICO it can be seen that the sales for the games are anything but fantastic however of all upcoming games mentioned on gaming forums, I always see the upcoming Team ICO game mentioned most times. Team ICO release a game every 4 years and the games dont sell well at all however Sony still have them making games which begs the question, why would Sony continue to support a team such as that?

To me it seems Team ICO are there for fan service and to give Sony a good image, there definitely not there to make Sony bundles of money unlike Polyphony Digital. 2/2 games are AAA so the studio is quality, that is for sure.

Sony probably likes the fact that Team ICO games push forward the "video games as art" debate.

Look, the sales for Shadow of the Colossus are incomplete. The game most likely broke a million pretty handily. Like... shattered it.

They keep on Team ICO because they make money and review well. The fact that they're the best team in the business is just a bonus for us, the players.

SotC sold very well. It deserves a lot more, of course, but it broke a million easily, plus it improved a lot on ICO's figures (700.000 worldwide, which isn't bad by any means).
And Sony knows that they give the company a very good image, and they might become system sellers for some people (not as many as GT, of course), plus if they are profitable (even if they are not huge money-making machines as GT) and become a leveraging option for people in choosing the PS3, Sony will continue to support them.

And of course, adding a guaranteed triple-A exclusive to the lineup isn't something Sony would want to avoid. After all, Team ICO is the best developer Sony has...and they will be one of the things that will make me get a PS3 in the future.

Well first of all SotC sold 700k in America only, Others and Japan sale figures aren't included so that kinda has a huge effect on how much the game has sold.

From what I understand, Fumito Ueda has near unlimited freedom at Sony. Of course, they probably know he'll ask for things in moderation, but Sony do look upon him as their top designer and treat him as such.

This is why I love Sony. They're not afraid to push bizarre, often niche concepts like Ico/SotC, Patapon, LocoRoco, and LittleBigPlanet.