No.
Firstly, Nokia isn't standing "at the edge" like many think they are (sensationalism sells). If I were to use your analogy, I would say they are heading towards that edge but are still a few miles out. Nokia has had some success in slowing down, but they have yet to change direction.
I do not believe a single device can save Nokia. So obviously I don't see the Lumia 920 as Nokia's sole savior. It will take many different devices catering towards many different markets to make that happen. I do think the 920 will be the device that nets Nokia a decent amount of consumer awareness in the U.S. (the Lumia 900 failed at that task).
Nokia's stock value may double or triple very quickly if the Lumia 920 sells well in the U.S. I'm betting on that happening within the first half of 2013, but they're very unlikely to return to the levels they were at a decade ago.
Either way, Nokia's return to competitive and sustainable profitability will be a long and hard climb, and it won't happen on the back of a single device.