Uhm. AFAIK it doesn't use base 16 or anything quite like that, it just has more bits with which to represent addresses, and it makes sense to show it SHORTHAND as hex. Today we could also have IPv4 as 'hex' by using hexidecimal 2-digits instead of xxx.xxx.xxx.xxx like we do. It doesn't change the base that's actually used, it's just that people are starting to describe it's sixteen sections (whereas we have four now) in hexidecimal to save time.