I kinda think this decision has already been made, and that's why we've seen who play how much in each game. As the starter, Ponder played sparingly week 1, and then through the first half in weeks 2 and 3. Then we saw Webb, the backup, come in for some much needed reps, and of course, start the final, week 4 preseason game. Sage gets a lil work here and there cuz we already know what he's got but still want to knock some rust off, and MBT gets to finish off the first and last game's reps, but doesn't get to play in the 2 middle games because there just weren't any reps left after we played the starters for a half or more.
In other words, I don't think Webb is going anywhere. Maybe, if MBT had looked a lil better, he might have replaced Sage, but 50% completions with 1TD to 2 INTs isn't likely to win you the job.
And, its not like everybody is looking for the Vikings 4th QB...most teams have guys in that spot who already "know the system." I'm not thinking he's looked so good that he won't make it through another year on the PS. Then, next year, when we've got a better idea of what Ponder can do, we'll have a better idea of whether we still need the "vet" or if we can go with the flyer with potential.