perhaps I can meet you part way, acknowledging the desirability of focal lengths up to 400mm for a certain niche of amateur 35mm SLR users, and hence of 100-400 (Canon) or 80-400 (Nikon) lenses for 35mm format. On the other hand, (a) this is a statement about 35mm format, and since Canon and Nikon offer nothing beyond 400mm for under US$5,000, that is clearly a rarely entered domain; and ( in 35mm format, wide angle coverage to 24mm and beyond is significantly more popular (and affordable) than telephoto to 400mm.
At the telephoto end, the counterpart of 100-400 in 35mm format is about 50-200 in 4/3 format, and since the Olympus 50-200 is smaller, cheaper and faster than 35mm zooms reaching 400mm, we should be able to agree that this is a desirable lens for that same niche of amateurs.
At the wide end, Olympus has an 11-22mm f/2.8-3.5 zoom coming soon, at a rumoured US$700, giving wide coverage comparable to between 20mm and 22mm in 35mm format, and they have also more vaguely announced a subsequent ultra-wide zoom for later this year (7-14mm, so reaching the equivalent of 13 or 14mm?).
In contrast, for Canon's amateur level DSLR bodies, the widest Canon zoom lens (16-35) reaches only 25mm equivalent, and costs about $1300; nothing wider has been announced or even hinted at. This seems related to Canon's intention to target "APS" DSLR's at low to mid-level amateurs, while expecting more serious photographers to pay the for now far higher price of 35mm format DSLR's, so that they are not doing much to accomodate some needs of more serious amateurs who use their smaller format DSLR's.