Kabby, I would think you either have to:
a) keep the existing stem alive all winter, in which case you have the best chance of seeing fruit next year
or
b) let it die right back to the ground as Cameron does and just mulch the roots very heavily to keep them from freezing. As she says, you probably will not ever see fruit if you do this, just a nice tropical foliage plant growing up from the roots each year.
Cutting the top off the existing stem will kill it anyway. May as well cut it at ground level. Bananas don't branch or re-grow so if you cut off the terminal growth, it will kill the stem. Wrapping anything in plastic for winter will also cause fungus and/or rot, almost always, because condensation gets inside the plastic.
To keep it alive all winter, I would think you'll basically have to either pot it up and bring it indoors, use the blanket and christmas lights method (which keeps the stem alive because it is kept warm at night) or build yourself a little temporary greenhouse around that plant. PVC pipe and heavy plastic (not touching the plant) should work for that purpose. You don't have to keep it warm enough that it keeps growing, you just have to keep the terminal leaves alive and the stem from freezing. Wrapping blankets around the stem won't really help in very cold weather because the plant itself doesn't produce any heat. So the cold will eventually freeze the stem if you don't supply an outside source of heat, like the Christmas lights.
Down here bananas basically just stop growing as soon as the nights get cool, and stand up fine unless there is a real frost (temps below 32 for a few hours at night) so most people don't have to take any measures to protect the plant unless a really cold night is predicted. Then, the trick is to trap the heat that rises up from the warm ground around the plant. We see tents of old sheets and blankets, plus piles of leaves around the stems to keep the roots warm. They perk up and start putting on new leaves again as soon as the nights are staying above about 50 deg.
Long story short, if you want fruit from that stem next year, you need to keep the stem and terminal (top) leaves alive.
