Actually, I don't think HDR is that difficult--especially with Photomatix Pro, a tripod, and bracketed RAW exposures. The only reason we even need HDR is because we're trying to compress dynamic range to fit within the output/display. Even if you could capture 16-stops in one exposure, one would still be limited with reproducing it. In essence, the dynamic range would have to be compressed again for display! Grad filters are actually an analog method for compressing DR--something that is easily done today in digital.
Not that I'm against improved sensors. I just think we're at the point that sensor tech advancement will be much slower because we're reaching physical constraints (lens resolution, manufacturing tolerance, et al) and the properties of light itself. I think there's way more that can be done with the AF system though. Good face detection for instance, is quite a neat trick! And whatever happened to eye-controlled focus? It worked well for me on the EOS 5/A2E.
Ultimately, I think the increased photo-site density (increased MP) will be more useful when combined with the ability to pixel-bin. This could result in markedly better noise performance and color accuracy at higher ISO. It would be neat if the 1D4 series would pixel bin for mRAW and sRAW, but I suspect research into that area is still in it's infancy. Who knows--Canon might surprise everyone.
There are but a handful of sports shots that could benefit from a 30+MP camera, but the majority would benefit from higher shutter speeds and better noise performance. Landscapes and architecture on the other hand would benefit greatly--I just spent a good admiring the work of Rodney Lough Jr. in one of his galleries in S.F. He uses an 8x10 film camera, and the gigantic prints show no grain at all. And the colors and resolution are stunning! Everytime he clicks the shutter, it's about US$50.
As for the IR flash control, I have actually used an ST-E2 for several years successfully outdoors in full sun. People assume because it's IR, it's terrible, but in practice, it works fairly well. It works fantastically well indoors. Obviously the RF PocketWizards have better range and doesn't require aiming the IR window.
I also much prefer the handy IR remote shutter release on the Rebel series (and the 7D) than having to plugin another corded trigger, but I'm not sure Canon will include that consumer feature on the 1D series.