Yes. It really is (finally) happening. This is a HUGE change for staff, 2HD or bow users that allows you to get the 5-piece bonus from 2 sets (in addition to the 2-piece bonus from monster mask/shoulder sets) when you use those weapons just like dual wielding and 1HD + shield have been getting all along.
This combined with jewelry crafting for all crafted sets will get the theorycrafter working overtime dreaming up new BIS meta for a while.
There is also a long comprehensive preview of all things coming with the Summerset update on reddit from one of the play testers invited to ZOS last week:https://www.reddit.com/r/elderscrollsonline/comments/89e1in/summerset_update_18_teaser_a_recap_of_last_weeks/