$499, imo, it would be a terrible mistake.
It's not a terrible price per se, giving it's more powerful than the others this time, but it would once again make the price a factor against everything they show, instead of being a plus.
It also puts Pro in a extremely good position, Sony drops Pro to $350 and their Slim to $200 and the people will notice that the jump from Slim the Pro is the same as Pro and Scorpio. So instead of being a disappointing mid gen upgrade Pro becomes the best bang for the buck, specially since the performance delta from Ps4 base(Or Xbone) is much higher than Pro to Scorpio.
Ms needs to be aggressive, not to try to turn the tables with Ps4, but to remain relevant.