Tripp in "CSI:Miami" actually isn't last, he's between Jonathan Togo & Eva LaRue, Adam Rodriguez is last.
I actually loved it when they changed the NY opening, Gary & Melina deserved to be put above the rest of the cast, their characters were/are the main focus of the show, as is Sela's "Jo".
CSI could always do an "NCIS", that is, after losing its original leading lady (Sasha Alexander) they moved the person credited after her (Michael Weatherly) into second and put the new leading lady third (Cote de Pablo).
I can see the credits looking like this:
starring Laurence Fishburne, George Eads, Jorja Fox, Eric Szmanda, Elisabeth Harnois, Robert David Hall, Wallace Langham, David Berman, and Paul Guilfoyle...
That is, if Marg is removed from the credits, they could keep her for, say 10 episodes, but have them episodes spread out over the 22/23 in the season, so she's in the credits for them all.
UNLESS they decide to make the show about the rookie's and put Langston & Brody (both CSI Level 2's, I believe) as the top 2.