McVay will probably be here for some years after Stafford.
But, I agree that the Rams are not going to go with spending a lot of draft capital for a rookie QB, and then waiting for him to develop.
They may have to go a year or two with a more journeyman type of vet QB, while waiting for their opportunity to pounce on a top notch one. But, I just can't see McVay or the Rams going the route of a rookie because 1) it takes time, and 2) you probably have about a 1 in 5 chance of getting a really good one. Terrible odds.