While Kolb likely will not play against the Seahawks this Sunday, there is always the possibility he plays in any (or all) of the next three games after that. The Cardinals know that he gives them the best chance to win as opposed to John Skelton or Ryan Lindley. And given the awful losing streak of eight games that the team is currently on, they know that they need to win some of these final games in order for both players and coaches to keep their jobs.
Skelton has been anointed as the starting quarterback for the team's upcoming game by coach Ken Whisenhunt, but he did leave the door open for Kolb to retake the throne upon his return. And if he is healthy enough to do so, I believe he should be thrust back into the starting job. Technically, it was his up until his injury, even if it was Skelton that lost it in the first place after hurting his ankle in week one.
The main reason I believe this is not only because Kolb is the best option the team has, but because the team truly does not know what they have in Kolb yet. Do they want to pay him the $9,000,000 salary and $2,000,000 roster bonus he would be owed in 2013? If he is going to provide them only 8 games per season, then probably not. It will also likely require a huge paycut taken by Kolb for the Cardinals to think about keeping him around.
Basically, Arizona needs to see that they can rely on Kolb to be "the guy" here in Glendale. So far he has not been able to prove that he can be. And if he can't prove that this year, he may not be on the roster next season.