Actually, a hookup with NW makes the most sense, which means it probably WON'T happen. Many if not most of the people currently in the Sand Castle have history in the Snow Palace, and the route systems would fit with some tweaking. The CFM powered Airbii in NW's fleet are among some of the oldest, with one or more already having been scrapped as it had exceeded the airframe life, so the new Airbii could replace those easily.
Now whether or not the combination is with the entire US, or they split East and West and combine those separately with other carriers, is another interesting question. As stated earlier, I think we'll see changes and combinations many of us never thought of, but suffice to say I think 2008 will see a major change in the landscape of this industry.
What has me concerned, however, would be to see the current crew running a yet larger airline--they have not demonstrated that they can handle what they already have......
My BEST to you all....