I read somewhere that only 2 or 3 other riders have ever won the tour at Lances ages so that is something to consider for next year, especially if some of his struggling (relatively speaking) this year is because of age.
If Ullrich, Hamilton, an some other key rivals are still on the upswing of their abilities, that would make for quite a challenge.
Meanwhile, I look at it this way. Six in a row would be great, but 5 at least puts him in first for consecutive victories and, I think, total victories. Just because he isn't alone in that position doesn't change that.