Some of the most dramatic lighting for outdoor shots such as landscapes can be when the sunlight momentarily breaks through a storm. If you're doing that, weatherproof gear is nice to have as a backup if the umbrella breaks...
The sensor is probably the single most expensive component in an SLR - why would what is likely to be the most expensive production Canon sensor at the time of release be put in a budget body? It'd still be an expensive camera, aimed at pros. Stuff like a minimal shutter lag, minimal viewfinder blackout and fast x sync (on full frame) are still exclusive to the 1 series, as is the rugged build to cope with years of use and abuse by owners who sees it as simply a tool rather than a treasured once in a lifetime investment - so why not put it in a 1 series body?
1.) I think professionals have already demonstrated that expensive cameras are not going to fly. But, Canon's main customers, non-professionals, will shut this camera down if it arrives with a 1D series body and price.
2.) Sensors do not add the expense the gullible public believes they do. The largest expense in a !D serties camera is marketing cachet.
3.) I think the vast majority of professionals shooting landscape in the backcountry (as opposed to overlooks
with the rest of the tourists) will want a small light body like the 5D2 which they adopted in droves.
4.) If someone is put firing away with a 50 MP sensor at landscapes and needs zero shutter lag. he/she may have purchased the wrong camera.
