Unmovable is a bit of an overstatement.
If you look at the cost of holding Romo's dead weight and paying the rookie QB something like $5M/year, the combined cost is still less than the current cost of having Romo on the roster. If he retires next year the combined cap charge for his dead money and the rookie would be $15.7M in 2017 and $13.9M in 2018. The charges for both years would be less than the charge the Bears are scheduled to take for Cutler, or the charge the 49ers are scheduled to take for Kaep.
Currently, Romo's charge for 2017 is $24.7M and it's $25.2 for 2018.
Furthermore, if Dallas can't afford to draft a QB then they can't afford to draft anyone because the contract is going to be the same regardless of who they pick. The rookie pay scale is perfect for grooming a QB. The prior pay scale made it impossible to even think about doing something like this with a pick this high. If Dallas hits on a QB at #4 they would have 2-3 years of good QB play at the cost of $5M/season. This offseason we saw Bradford go for $17.5M per year and Osweiler go for $18.5M per year. RG3 went for $7.5M himself. Even if Tony played 2 years, the Cowboys would have 2 rookie contract years and the 5th option year. Call it $20M for that 5th year. Looking at $30M total for 3 seasons of QB play so $10M/season, on average.
The drafted QB wouldn't even have to be all that good to still come out on top in terms of getting good returns on your dollars spent. The break even point would probably be somewhere around the 20th ranked QB, and 5 years from now it will undoubtedly be lower. $10M/year will be an absolute steal in 5 years for a QB who's just mediocre.
That isn't to say the article isn't right in some aspects. Having Tony retire or get cut will hurt. If Dallas drafts the QB and Tony retires after 2016, there's about $10M/year for the next 2 years that is doing nothing. That's 1 damn good player at any of a number of positions, or 2-3 solid starters. I can't even remember the number of times I saw various posters say that the Seahawks were competitive largely because they didn't have to pay market rate for their QB. Stuff like:
If that's the case, Dallas has a perfect opportunity to lay the foundation for a dominant team by getting a QB at a price that wouldn't be possible on the market. The ability is dampened relative to Seattle's based not only on draft position, but also on the fact that a player like Richard Sherman wold largely be covered for 2 years if only they had access to Tony's dead money. The point remains, the opportunity still exists.
There may be reasons to pass on a QB, but the cap damn sure isn't one of them. In fact, if all you could get out a QB at #4 was an average QB, you should heavily consider pulling the trigger. You'd essentially buy yourself 5 additional years to find a legitimate star at QB and all the while you'd be able to use more resources at other positions to help build the team. The Chiefs are competitive with Alex Smith. If you tell me I would get nothing less than a bus driver like Alex Smith, I'd take it in a heart beat because it would allow me to build around the QB position so once a more capable player is found everything is in place to contend for a title.