No NW will not get the 737NG because the AIrbus 319/320 seats just as many, flies just as far and is just as comfortable, therefore it would not make sense.
This type of post keeps popping up more and more, i.e. will DL get AIrbus 320s? Will UAL get 737NGS?, Will AA get Airbus 320s? etc etc. I hate to be one of those posters that tries to censor others, but apparently some posters haven't figured out if one airline is operating or buying a certain type, they aren't going to go out and buy the other type offered by the other manufacturer and duplicate themselves, at least in the US.
SO: Any US carrier that is taking deliveries or who has many Boeing types on order for a specific nitch, will not be ordering the Airbus counterpart.
Same other way around, any airline that is operating, ordering or taking delivery of large quantities of an Airbus type, aren't going to go to Boeing and order the counterpart. It is too expensive and doesn't make sense.