This sounds like an anti-Canon tirade, which would be unfair based solely upon a rumour. Let me just state that I'm not buying any camera equipment until all the major players show their hands this year and then I will be making a long term decision on whether to stick or switch. I'm pretty sure that I won't be the only person in this position.
I'm with you 100%, and no, you're not alone. I've already researched how much of a hit I'd take on my bodies and glass, and if the 5DIII doesn't stack up well to the D800, I'm jumping ship. I currently shoot with a 1DsIII as my primary body, and a 5DC is a backup. Overall, I'm very happy with the 1Ds, but would just like some more resolution, DR, and high-ISO performance. A few more FPS would be nice, but 5 is enough for most situations and the AF works very well. I'm sure the 1Dx will address most of these issues, but at $6,800, I'd be paying for speed (12-14 FPS) that I don't really need, while still pining for more resolution. I have no doubt that the 1Dx will be have stunning low-light capability, but if that was my top priority I would switched to Nikon and bought a D3s a long time ago.
That's where the D800 comes in. If the rumored 36 mp sensor actually materializes, and it's DR and high-ISO abilities are merely on par with the D700, I see it as an upgrade over my 1DsIII. I don't care that I'd technically be "downgrading" from a pro to a prosumer body. I'm sure the times where I miss the 1D's tank-like build quality will be offset by the times where I appreciate the D800's lighter weight and smaller form factor. The D800 would simply better suit my needs than a 1DsIII or even a1Dx, and I'd save a bunch of money to boot.
The big wild card is the 5DIII. If it specs out as a high-resolution, compact body with a much-improved AF system, then I'll stick with Canon. If it specs out as a 1Dx Jr. with the same 18 mp sensor, but with a castrated AF system, then all my Canon gear is going up on ebay.