That sounds a bit disingenuous. IPv4 was always on a forced rotation because a) limited address space and b) ISPs wanted to milk customers for static IP charges. IPv6 eliminates a). That leaves b) which isn't really a factor on mobile devices. It really is a permanent cookie if the ISP decides to implement it that way. I can't say I trust AT&T and Verizon after their 'header enrichment' shenanigans.