Initial tests of the 3070 show that even the AIB models with good cooling have very limited OC headroom, of course for the cost of increasing power consumption noticably. If this is any indication to Ampere's OC-ability, it would be reasonable to think bigger brothers also have poor OC potential.
On AMD's side, rumors suggest that RDNA 2 may offer a very good OC potential, at least for AIB designs.
Nvidia cards don't draw a good picture on power usage, OC headroom, availability so far. Let's hope RDNAs offer a good competition, forcing Nvidia to price-drop or come back with revised products. Competition is good for us.