Do you have a referece to when this prediction was first made?
"It appears that the amount of DNA in organisms is more than is strictly necessary for building them: a large fraction of the DNA is never translated into protein. From the point of view of the individual organism this appears paradoxical. If the purpose of DNA is to supervise the building of bodies, it is surprising to find a large quantity of DNA which does no such thing. Biologists are racking their brains trying to think what useful task this apparently surplus DNA is doing. But from the point of view of the selfish genes themselves, there is no paradox. The true purpose of DNA is to survive, no more and no less. The simplest way to explain the surplus DNA is to suppose that it is a parasite, or at best a harmless but useless passenger, hitching a ride in the survival machines created by the other DNA."
(Richard Dawkins, The Selfish Gene (1976), pp. 43-44)
[emphasis mine]
The irony of Dawkins noting that biologists were 'racking their brains trying to think what useful task this apparently surplus DNA is doing' was that he apparently felt no need to engage in all that strenuous mental effort himself because he had already reached the conclusion that the 'surplus' DNA was 'useless'.
Cordially,