Iif they ditch the RT
That, my friend, will never happen... the RT is BMW's second best selling bike world wide and the best selling bike for them in the U.S. That would be like Honda getting rid of the Accord or Toyota axing the Camry... it sells too well. What may happen though is the boxer power plant morphing into a liquid cooled configuration down the road.
What BMW needs to examine is there a market for a luxury tourer here in the U.S., the LT's primary market? I think so as Honda moves a lot of Gold Wings. The other brands are not going after this market at all (unless you count cruiser/dressers, which I don't), so it leaves just Big Red and Big White and Blue to compete.
I think the scuttlebutt is that the LT is due out as a new model in 2010. We shall see.