i think a two hour season finale would be the best way to go about it, because the lag due to harry potter and millionaire would give right crappy ratings for a finale (not good in a sweep month either).
last year the finale was finished shooting on jen's bday, and it looks like this season is following the same sort of pattern. So if it airs on the 2nd that give a week and change to score, edit, etc. thats pretty good for a pinch anyhow.
PS phase one and the telling were both done on really tight schedules last year