If I looked around I could find a quote from Chris Carter on writing that says something to the effect that what's important isn't so much how it ends as how you get there. And you don't want to get locked in too early because you'd miss learning things along the way.

Just because a series creator has a clear ending in mind right from the start doesn't mean it will be what the fans wanted. It certainly doesn't guarantee that it will be any good. The Battlestar Galactica reboot people knew where they were headed and most of the fans hated the ending of that series. The ending of Lost was pretty controversial. I thought the last season of Fringe was pretty terrible and season four wasn't much better. Farscape had a pretty terrible conclusion, which the after-the-fact miniseries didn't really fix.

Anyway, signs are good that CC and 1013 are going to get another shot at ending the series. Maybe this time, they'll get it right.