It's not likely that anyone will produce a 24 - 105mm f/2.8 IS L.
That is likely what people were saying in late 80's when the 35-70mm f2.8 was being made, and again in the mid 90's with the 28-70mm f2.8, and now with the 24-70mm f2.8. Look at the progression, what makes you think it will stop?
20-35mm f2.8 (1989) -> 17-35mm f2.8 (1996) -> 16-35 f2.8 (2001)
28-80mm f2.8-4 (1989) -> 28-70mm f2.8 (1993) -> 24-70mm f2.8 (2002)
80-200mm f2.8 (1989) -> 70-200mm f2.8 (1995)
On top of that we could add the Nikon 14-24mm f2.8 to UWA list, and the 35-70mm f2.8 to the Normal list. Also, we could look further back in history with the FD mount: (24-35mm f3.5  -> 20-35mm f3.5 ). Constant aperture zooms have grown from less than 2x (24-35 is 1.46x, for example) to 5x (Nikkor 24-120mm f4).