Port numbers is only useful and needed if you are dealing with carrier NAT. That is NAT performed by the ISP, such that multiple customers share the same ISP. This happens to be somewhat common with apartment networks.
If RIAA/MPAA records the address 2001:db8:a55:beef::2af6 only the "2001:db8:a55:beef" part is actually useful. The remaining part of the address will typically be a randomized privacy extension address. They are therefore still unable to prove which machine was used to download the content.
If you are one of the persons that want to use easy to remember addresses, you can still use privacy extensions. With IPv6 it is normal to have many address on each computer. You can have your easy to remember address (2001:db8:a55::2) that you use for ingoing connections. And the machine will prefer the random privacy extension address for outgoing connections (2001:db8:a55::9b43:82dd:2239:10bc - right now but in an hour it will be completely different).