If Sammy Peter loses to Oleg Maskiev, will he be considered a former WBC Champion?

Well, he won the fight so he is now the "full" WBC heavyweight titlist. If he lost he would not have been considered a former champion because he never actually held the WBC title until he beat Maskaev. And you are correct, so far he has only fought Wladimir and lost a decision, but the putrid WBC is enforcing him to fight Vitali now because, long story short, when Vitali retired he was promised an automatic shot at the WBC title if he decided to unretire, and since he is coming back, they are enforcing his fight with Peter (the new WBC titlist). Personally I would much rather see Peter fight Wladimir again because that would give us the first TRUE heavyweight champ since Lennox Lewis retired.