This is trivial, I know, but I found it interesting:
When I was up on delta.com, I was looking at the seat maps for the 737-800.
They include specs on the height and wingspan of each aircraft in their fleet, along with a graphic.
If you look at the graphic showing the height of the plane, it clearly shows a 738 with the new winglets.
See for yourself: http://www.delta.com/travel/maps_guides/aircraft/b-737-800/index.jsp
Look about 1/2 way down the page, middle graphic, above the seat map.
Is this in the cards for DL?