Nope. Data from actual raids says Frost scales much better than Unholy.
Some of that is, of course, sample bias. The "top spec" for any class gets the best players, with the best gear, playing it. But that only applies to the gap between Frost and Unholy. Frost scales well compared to other DPS specs also.
Again, that doesn't mean Frost performs better than other specs-- it's middle of the pack, because its base numbers start lower. But based on this scaling data you would expect Frost to continue to be competitive in future tiers. Unholy, not so much.