Indeed, they've been using the 737NG image since 2008, and surely for marketing purposes as you said. However it wouldn't surprise me if the 737NG plan was called for in the Business Plan but since the financial turmoil started in 2008 they ditched the plan and chose to keep the image, again for marketing and promotion purposes.
In any case, it is deceitful, unprofessional, and atypical for any civilized company.
To add insult to injury, they've been sporting around the photo at the Dana Crash press release hall.....Right behind the crying Jacky Hitharamani