My opinion is this:
Firstly, I think this is an incredibly mediocre year for quarterbacks, therefore I wouldn't be looking for a Romo replacement this year.
Secondly, I think that most of the guys they've looked at - like Petty and Grayson - would be 'bonus babies', not allocated for given their current allotment of picks, but ticketed as options if additional pick are acquired via a trade down.
Essentially, the only way I feel that either of these guys is a Cowboy would be by virtue of trading down in round one and getting another pick to use on a QB.
Thirdly, I think the team is in 'win now' mode and utilizing any premium draft pick for a guy to hold a clipboard flies directly against that.
And fourth, considering the huge contracts quarterbacks now command, teams like to maximize the time they have one 'working on the cheap', and drafting a guy to sit for two to three years effectively uses up their 'inexpensive time' and even if they pan out, you're right back to paying huge money for your quarterback.
So, with all of those factors, I'll be surprised if we see the team drafting one this year before round 7, barring that trade down I mentioned.