Depends heavily on too many factors. What type of game? What type of object? How big is the object? How close will you get to the object? What else is on screen? How much resources are spent on AI, physics, animation, sound, etc? What hardware? Tablets can vary a great deal etc etc etc
Really comes down to the tech you are using, tablet/mobile generations you are aiming for, etc. There are just so many factors that come into play, that you really need to do your own benchmarks. When I was working mobile, we tried to get our hands on as many target devices as we could as not only does the hardware differ…