Whilst I'm not expecting anything much to be announced by Bachmann this year, there are two steam locos that I'm amazed no-one has done in RTR yet: the SECR D and the GER J69.
Both offer many livery options and have ornamental as well as operational value.
With the D class, it should surely be possible to use the chassis and tender for a D1 too, opening up more sales opportunities, as well as shifting more Birdcage coaches?