The description seems to imply it adjusts damage to the current level; is there better gear (or rather same gear but with higher stats) to be found on NG+?
There are 'Legendary' versions of all the Witcher gear and upgrades in New Game + with appropriately higher stats. Other gear you find will also have been scaled.
I haven't seen any comparisons of how Aerondight compares to these however my Aerondight is still good at level 84 (but I did get it while already playing New Game +).
If you have the Hearts of Stone DLC you can also get the Runewright to add sockets to the sword to make it even better.