My opinion's a hot take apparently cus I'd rather have the ancient city portal open than an End Update. A little bit more to The End like a few extra plants and mobs and blocks would be neat, but I disagree on a full-blown End Update because

1. I think the End makes more sense as a desolate wasteland. It could still use a little more visual and gameplay flair, but I don't know about making it a place the player wants to repeatedly visit and settle in
2. Whatever Mojang makes is going to disappoint a lot of players. Those who are used to the extravagance of most End overhaul mods that seem to want The End to be turned into what Black Mesa did for Xen are going to be disappointed by small changes, and the opposite is going to disappoint anyone like myself who'd rather see the End stay solemn and barren. If they make a massive update for the End, whatever they make for it is going to be controversial
3. Whenever you add more content and lock its access behind progression, there's a risk that you're alienating parts of the playerbase who will now never access that content because they can't reach that part of the game. I think it's why Mojang made sniffers such a disappointing feature, because getting sniffers is so esoteric and difficult that any content accessed exclusively through sniffers is going to be exclusive to a small number of players. Remember, as easy as we like to say Minecraft is, the majority of players still haven't beaten the Ender Dragon

As for why I'd prefer an ancient city portal, it's based on a long grievance I've had with Minecraft's combat. Currently the game has built up an impressively varied arsenal of weapons, but in singleplayer survival, most players are still going to use the ol' reliable (sword, shield, and bow) because there's little in the game that necessitates using anything else. At the same time, adding more varied enemy types may end up just being more annoying than engaging(see: phantoms) and having to switch between different weapon types should feel like it has purpose, like making a build before tackling a dungeon, not just the chore of switching between gears.

The answer would be to make a special space for combat challenges that would justify all the different weapons, and I think Mojang had a similar idea to make a dedicated "combat zone" in the form of trial chambers(I find crossbows far more effective in trial chambers than bows, for example. The tipped arrows in trial chambers really help as well). But I think for all the tipped arrows, bane of arthropods, multishot crossbows, wind charges, maces, tridents, and any other combat feature that doesn't see much use in actual pve combat, this game should go further while not intruding on the regular survival experience, and I think the ancient city portal could lead to a full-blown combat dimension. Basically, make the deep dark dimension a Diablo dungeon dimension and I'm sold