Upload & Sell: Off
I don't think Nikon and Canon are waiting for each other to make the first move then announce their offering. These sophisticated cameras, if they exist, must have been designed quite some time ago and have been tested in the field for months and months, it's not something they can pull out of their hat quickly after their competition announce the new model.
I agree, however both Nikon and Canon customers have been waiting many years (far beyond a normal refresh cycle) for a replacement, and there is a guaranteed market there, but neither company has delivered. Pretty well every other camera has been updated, even the 1 series and Coolpix lines, and a couple rounds of FX cameras, but not the D300 or Canon 7D. I'm not sure what the reason is, but I don't think either company wants to be first unless they know it'll be a winner. Who knows though. All I know is a lot of people are going to be happy if we see a true replacement, and it would be so easy to make, entirely out of preexisting parts (D7100 sensor, D4/D4s AF, appropriately sized buffer, Expeed 4, D800 body/controls/meter, 8FPS/9-10 with grip). Boom, done. Sell for $1999 or even $2199 and rake in the profits. Those would fly off the shelves, but there has to be a reason they haven't bothered yet.