Most sites that have found the need to implement bans by address consider this collateral damage to be worth it - in fact to get around it being difficult to IP-ban someone on an ISP that hands out variable addresses some will ban a whole range (first banning one address, then another, then another, and after several addresses in a range (something like a /20 or more - a /24 would not cover all but the smallest ISP's dynamic address pool) are banned the whole range gets the hammer, at least temporarily.

IPv6 will make a difference if its adoption means that the use of NAT drops considerably, but even if every device really does have a unique address there is still the problem of several users on the same device (implementing per-user addresses on a single device is never going to happen as it is just too much hassle for little or no gain).