The only negative I see with this signing is that even after Dallas signs Dak, when he has a bad game, this site will be barraged with "Dalton should start" posts. Since some are already saying it, we probably won't even have to wait until a bad game. Some will be crying when Dallas signs Prescott to a market-value deal, which is what they will eventually do.
There's only a slim chance that a deal doesn't get done because Dak wants too much. Again, like with Lawrence last year, what's happening right now is just typical for negotiations. Neither side bends until it has to.