Well, at least that's the consensus opinion, because the Vikings never announced whether they were or they weren't. The deadline was yesterday, and they made no announcement that they did pick up the option...which means they did not:
No surprise: Looks like Christian Ponder 2015 option definitely not picked up. 11 p.m. CDT deadline passes and no Vikings announcement.— Chris Tomasson (@christomasson) May 3, 2014
One of the new wrinkles of the CBA that was ratified in 2011 was rookie contracts being four years long with a fifth year option, giving the team and players more flexibility. The fifth year option salaries are fairly straightforward, and are explained pretty well right here. Basically, if the Vikings had picked up Ponder's option, who was the 12th overall pick in 2011, they would have owed him what the average salary would have been for the third through 25th highest ranked quarterback salaries in the league. Had he been a top ten pick, his salary would have been the cost of the transition tag for the QB position. Both numbers are hefty sums for a backup (Chris Tomasson of the PP reports Ponder's 2015 salary would've been just under $10 million), and there seemed to be no way that the Vikings were going to do that.
In the end, they didn't.
So the Ponder era will end with disappointment and a new quarterback running the show, which after the way things went down with the QB position in 2013, shouldn't really come as a surprise to anyone.