You know, I sincerely hope they don't. I think it's to AMD's (and ATI's before them) great credit that they've tried to avoid getting caught up in the temptation to smear an opponent's products, preferring to concentrate on making their own better. The last thing we need is for the whole graphics market to devolve into a contest to see who can sling the most mud. Plus I don't see how it'll help - it won't stop the rabid nvidia fanboys slating AMD and bigging-up nvidia (in fact, it'll just give them another thing to moan about), and it might put some of the AMD fans off if AMD appear to be turning into a spin-and-smear company.
It's also worth pointing out that one potential influencing factor in nvidia's current behaviour is that their developer relations program - once their strongest suit in the gaming graphics market - is falling way behind AMDs. I remember there was once a time when well over 50% of the games in any given graphics review would be TWIMTBP titles, while you were lucky if even one was from ... well whatever ATI's equivalent program was called (yes, it was so unsuccessful I can't even remember its name!). Now there are more Gaming Evolved titles than .. again, whatever nvidia's current program is called (is it still TWIMTBP?). AMD have all the major consoles, they have Mantle coming out, they have a very successful developer relations program - they don't need to resort to slinging mud. They're sitting on the key software stack for the next several years of gaming development.
If nvidia want a slice of that pie, they're going to have play nicey-nicey at some point. AMD just need to wait 