Here's when certain Destiny 2 weapons will reach Max Power Level limit

[Windows Central]

You'll need to find new favorites.
A few weeks ago, Bungie announced that it was adding Power Level caps to legendary armor and weapons. This means that many of your favorites, even Ritual Weapons from the looks of it, will be essentially useless for high-level activities because they won't be able to be infused to a higher Power Level. The Max Power Level will be set at the Player Power Cap attainable three seasons after their release.

Full story from the WindowsCentral blog...