Cyberway: Now that the game is confirmed to the be in development, would it be fun if it was 100% Urban? Nothing but big massive City. Maybe a bit of outside, if it ever got under siege during story etc.
Problem is, The Witcher has a medieval setting, which greatly limits the size of the city. You'd have to expect about twice the size of Novigrad at most. You'd also have to rely exclusively on herbalists if you want alchemy and bomb making. There's only so much variety in cities, after all.
Another problem is the limit on monster variety. Where would you find a Leshen? A Rock Troll? Echymaras or Arachnomorphs? What about all the Draconids, like Griffins, Forktails, Wyverns, etc.?
There's also a limit on how many monsters you can fit in the city before the story loses credibility. There's no way a city could possibly grow to twice the size of Novigrad if it had even half as many monsters as all of Velen or Skellige. Just look at how many monsters Novigrad had: 1 Succubus, 1 Doppler, 1 Godlin, 1 Nekker (smuggled in), and 1 Vampire. The rest had to remain in Novigrad's sewers. I don't mind going into the sewers for a dozen quests or so, but to have a game the size of The Witcher 3 and have half the quests in the sewers? I wouldn't like that very much...
And finally, designing cities is a lot of work. Unlike a natural landscape, which can be procedurally generated (then manually polished by adding towns, roads, camps, etc.), a city has to be built by hand from ground up (at best you can generate the layout of the land, but all the rest of the man made structures must be placed by hand). Most people don't really realize this, but making games is already a ton of work by itself. I know, because I've actually made some (or tried, at least). So what does it mean? It means that increasing the effort needed to make a game will increase its cost (more developers working on a game for longer time periods). And since most people wouldn't willingly pay more than $60 for a game, the game would need to sell more copies. This is essentially a form of gambling: do you increase the production costs in the hopes that it'll sell better?
Rockstar North can afford to make these gambles, because they've pretty much established a reputation for high quality games. All they need to do is announce GTA 6, and people will buy it even with minimal marketing. CDPR is not nearly at that level. While The Witcher 3 was a good game and well received (despite the bugs), it's not nearly as famous as GTA. Meanwhile, Cyberpunk 2077 is currently extremely polarizing, and the recent refund campaign on PS4 and XBO is not really helping CDPR's reputation.
Therefore it's extremely unlikely The Witcher 4 will be 100% urban. There's just too many problems to solve, it would make development cost skyrocket, and offer no apparent benefit. As your thread clearly demonstrates, there's simply not enough people who care about a 100% urban Witcher game to make up for the increased production costs. As it stands now, only 1 in 6 people would buy a 100% urban Witcher, and let's be honest: you'd probably still buy The Witcher 4 even if it was set in Velen, Skellige and Kaer Morhen (and Toussaint) again, so why bother?