I don't think that's going to be a problem as I think Kiefer Sutherland is currently serving a prison sentence for his drunken driving escapade, and I believe they said him being in the slammer wasn't going to affect production.
You do have to keep in mind that it's the writers - not the actors - that are on strike. The majority of filming's been done already and most shows have the ******* to make it through the season. It's the talk shows and soap operas that are going to suffer the most early - the impact will be felt on weekly serials starting probably next season (if the strike goes that long)

