I'm noticing a lot of people who are voting "No" are not considering what's coming up in U48 either.

Yes, Vengeance 1 was a new thing and could be seen as a test: bringing everything to absolute bare bones to see if performance is good. They spent so much energy trying to stress that this was not a solution, but only a stress test. But people did enjoy it for what it was.

Vengeance 2 added weapon lines and people liked that, since a lot of players use weapon skills in their builds as well. Again, it seemed to go well (but there were already some creeping reports of heal stacking getting problematic)

Now Vengeance 3 didn't exactly add much new stuff - the biggest thing is meatbags that don't leave a ground AoE. Guild and Armor lines are not as commonly used, so a lot of people are thinking that it's pretty well the same thing as Vengeance 2, but without the Golden Pursuit or AP bonuses we had before. That's the main reason that it seems uninteresting is that the incentives are not there, and it's competing with a PvE-focused event that drops expensive style pages.

Still, seems like just a test... until we look at U48 and Vengeance 4.

There was barely any work done at all in post-Subclassing balance. Why did the team, knowing how unbalanced everything was since the players tested it on U46's PTS, not really try to do anything to general Class balance at all? Well, it definitely looks like all of their effort since dropping the nuke that was Subclassing went into making Vengeance into a brand new mode.

Vengeance 4 in December will be bringing "loadouts" and "perks." So... what's that? Those are not seen in any other mode, so why did they not only add something that doesn't exist anywhere else to 'test' it, and why did they get that art team to make a brand new UI and icons fir all of it? It seems like "loadouts" is closest to food buffs (so why not just give the template character a few food choices and be done with it?) and "perks" are closest to CP bonuses (so why not just activate some CP nodes?), but each also is very tailored to a Cyrodiil game mode. And we're supposed to believe that they had no problem making brand new assets like that for just a test that they're going to throw out later? No, that's 100% prep for a new Cyrodiil campaign. They are making a permanent version of Vengeance, which is going to use those assets. I still believe they're not going to replace Grey Host, but Icereach and likely Ravenwatch will be going.
(and it does feel a little bad that the U48 preview stream said they're planning a Vengeance 5 early next year which will try to balance the Vengeance abilities as well. Note that balancing the rest of the game was not mentioned...)

But really, why keep this hidden? Just come out and say "hey, we're getting a lot of positive feedback from Vengeance, so we want to make it permanent next year! But don't worry PvPers, we're not removing Grey Host!" That would definitely stop a lot of the angst about all of this.

Also, if it were still "only a test," then logically they would be able to table it for an update to focus on general balance if it were that bad. They did tell us that the theme of this year was to "not rush content and give everything the time it needs" after all...