Since you have updated the F7 to include a dcc decoder, I wonder if there might be plans to do the same with other "older" diesels such as the GP50 or the GP40/B23-7?
Bachmann's current business strategy is to put a decoder in "everything" n scale.
If, and when, Bachmann re-runs "older" locos you can bet they will have decoders as well.
A new version of the GP40 was released earlier this year. Unfortunately, it is not available with a decoder (although it's a bit more DCC-Friendly than previous versions) -
(http://www.spookshow.net/loco/files/bachgp402018mech1.jpg)
-Mark