Of course it would depend on the wording. If it is simply a tack-on to the existing, to wit "...engaged in the business of dealing firearms, exempting anyone who makes occasional sales, exchanges, or purchases of firearms for the enhancement of a personal collection or for a hobby, or who sells all or part of his personal collection of firearms ...unless the total sold exceeds 50 firearms per year" then it would measurably inconvenience a few folks.
If it is merely a restatement of the definition to be, "...engaged in the business, defined as selling more than 50 firearms in a year" then that would allow a certain degree of relief to those who get mighty nervous about selling a few guns now and then, but who knew they could always be painted with the charge of dealing because the law is so vague.