On the chance this rapid warming does occur, the question becomes: Will we see an El Nino for this winter?
If we see the SST's warm enough, then yes, we would see an El Nino. There are numerous caveats with the premise of an El Nino this winter, but I've already explained a few of them above. What we really care about is- would this El Nino transfer into the atmosphere? Based on current projections, I would not think so. Current model forecasts and analog years suggest a cooler than normal upper US, whereas an El Nino would bring about a warm trend throughout the Plains and Midwest.
Time will tell if we actually see an El Nino develop, but right now, I am skeptical of the idea.