'better optimised' currently yes, due to the fact that other graphics cards still experiencing problems with mantle. But that's not AMD's aim, the aim is to benefit their entire range with possible more emphasis on lower end cards.
Out of the box you will no doubt get much better performance and the fact that with my 7950, mantle works, I don't doubt it will work for the 7970.
I would say though, I wouldn't advise using ultra settings - not because they're too demanding (I personally haven't played too much with it on), but the fact that the difference between high and ultra isn't massively noticeable at all, and for the sake of a good 5-10 fps, I would not advise it.
But of course, that's for when you get your new card