Most likely, Sansa will have learned her lessons well, and pay her debts when she reveals herself at her wedding to Harry the Heir. If Littlefinger had one weakness, it was for Catelyn and now Sansa.
Karma's a bitch. Now we just have to wait for Littlefinger and the guy who tortured Theon to get their turn. Then again, I have a feeling George favors Petyr
I can't imagine that Littlefinger will get his until the very end. If anyone in this series is the main bad guy, I bet it's him(not counting the Others because they're more of an evil force than actual characters).