I typed out a long response, but my internet connection timed out. Here's a summary. With Penny's injury, the rotation looks like this:
When Penny comes back, it will look like this:
EDIT: Out of these 5, Alvarez is the most likely to be demoted to the bullpen if Ishii comes back into the starting rotation. As of right now though, Tracy seems pretty intent on using these 5 starters for the remainder of the season
When Jackson comes back, he might take Alvarez' place. If Nomo comes back strong, he could also be a candidate to replace Alvarez. Ishii's inconsistancy has landed him in the bullpen for now. The only reason why he's starting is because Jim Tracy doesn't have any other viable options. Unless Ishii pitches lights out until Penny comes back, he'll return to the Pen.
Nomo's return could make it interesting if he pitches well though...
That's my $0.02, and that's the word on the streets here in LA.
[size=10]"Men are apt to mistake the strength of their feeling for the strength of their argument." [/size]