Well they are also nerfing BHammer and it is confirmed to be left behind. We don't know yet but it's very possible that they want to create a whole new sandbox of top end gear.
Nerfing the old gear ensures that it's not too OP. The weapon updates are mostly nerfs.
People tell me that the FF MMO does this every six months and you never get to "upgrade" the old stuff to the new maximum.
The difference with MMOs that do this, is that you just chase the new gear with similar, or the exact same stats/perks/armor rating.
If for some reason they don't have some new "fate bringer", "vision of confluence", "black hammer" type perks on similarly typed weapons, it will be one of the dumbest moves they could possibly do.
Hell, it's already dumb to make all the old weapons obsolete.
The problem was never a "meta" game, it was that Bungie didn't make enough crazy perks for new content to warrant switching to the newer gear.
If Bungie came out and said;
"Here is a sneak peak at one of the Dragons you will be chasing"
And preceded to show a hand cannon that every 3 precision shots sent a blade dancers razors edge in the direction it's fired, we would be a lot more keen to leave the fate bringer in the dust been.
But no, we got the Crota hand cannon, and the jewel, and the dreg pistol.
None of these fill the void of what the fate bringer brings to the table.
New gear should give us a reason to want it.
Raid gear should feel exotic.
Black hammer was good, as well as almost everything from VoG.
Everything after that is "meh, I can use it, but it just feels like this gun with an element".
This ruined most of the rewards for both Crota and PoE for myself.