Do you think the meta will change after the update?

Doubt it , although weapon refinery might see eldigan and Ephraim become more popular.

Yeah I'm waiting to come back to the four Takumi teams, before inherate that was quite op.

Weapon refinery will be a huge power creep, just like inheritance and sacred seals, its an extra skill slot.

I don't think it'll change things drastically, but there'll definitely be changes.

Weapon Refinery should help a bunch in balancing out the powercreep. Not sure I'd call it an outright answer, seeing how material grinding will be involved, but it'll definitely be helpful.

I'll be interested to see if the new 5* healer skills will bring some healers into the Arena.

It's too early to call whether or not there'll be a return of the Reign of Takumi, as we don't know what upgrades he'll have access to. Maybe it'll be a Fury effect... or maybe it'll just be Obstruct. :P

I think it depends on the player and if they're willing to build their units more than they need to.

Yes, it will change. Specially with Killer weapons being upgradable to Slaying weapons, with Quickened Pulse/Infantry Pulse we may see fully charged Moonbow/Glimmer at first turn. I think we will see this one in units with Distant Counter and high Atk or Bonfire/Iceberg with high Def/Res (specially with the +4 in Def or Res a upgrade can give).

The effects from Weapon Refinery will add interesting things to the table, Ephraim doing a follow-up with full HP and his high Atk plus the buffs he can give makes him more useful than before. We need to see the other weapons effects to see how powerful they become.

And yes, they will fight powercreep because some of them rely on Legendary Weapons. Having a "normal" unit with an upgraded weapon will give a very useful boost to compensate the higher BST these units have, also that will make them very reliable (like having a Sheena with 40 Spd).