Yes, but they know what they want to put in the book, and don't go overboard and waste time designing things that won't make it into a book if they can avoid it. Ravnica had 3 playtest subclasses in Unearthed Arcana, the Order Cleric, Spores Druid, and Brute Fighter. The Brute Fighter was dropped because it was too similar to the Barbarian.
No, it was just not a thing. This is something that crept up from the movie makers. Using non black to play black people and it had a racist connotation to it. It was often done in the previous decades but now, it is viewed as a bad thing and unartistically thing to do. I had a few friends from oriental (china and vietnam) that were quite pleased that the hobby had given them a chance to play a bit of their culture. Of course it was not perfect, it was done from a western point of view after all. But it was better than most people think. They are judging from today's perspective and they do not try to understand that time's perspective dismissing it as a bad thing. In 20 years from now, our own perspective might be view as a bad tasteless thing that was archaic and close minded. Perspectives change over time. What was good a decade earlier will be bad two decades later and three more decades and it will be good again. Such are the wheels of history and its perspectives.
They can try to make money without taking the easy way out for it. Magic: the Gathering settings are easy, so they'll continue making them. I know a lot more people would prefer Dark Sun to a M:tG setting, or a brand new setting altogether.
Yes, I don't think Planeswalkers should be in D&D. There is Vi, who could be a planeswalker, but this opens more questions than it solves, IMHO. I don't think Elminster or Mordenkainen are planeswalkers. They haven't been to any M:tG setting, probably have no idea what the "Blind Eternities" are. I think the best explananation of their traveling to Earth and other worlds are Sigil or Spelljammer, or a high level spell that lets them teleport.
It's not the theme of the worlds, but the fact that adventures there are largely overshadowed by centuries of convoluted lore, planeswalkers, and the fact that Magic colors have no terms in D&D. I like the theme of New Phyrexia, but it wouldn't be a valid setting in D&D for a book, IMO.
Yes, but any action of the players will be overshadowed by a storyline in an updated Magic block. GGR was released, and then the War of the Spark happened. This opens up a lot of issues of, "What's lore?" and "When are we?" and "How do we deal with this?". Sure, this can be solved by the DM, but that takes a ton of work on the DMs part, much more than any other 5e D&D world.
This is purely speculations but I do believe that a plane book is coming. A lot of the UA classes could be thought of as outer plane related classes. Your theory is as good as any. Nothing prevents them to test multiple classes for multiple books over a year. I don't see why they should restrict themselves with only the next year's books. A book can take two or three years to build up correctly. So testing a bit of the subclasses they think of including is a good thing.
Yes, there's no reason why the playtesting of a Planescape subclasses and a Theros subclasses UA can't intersect. A larger amount of player options in a book requires more time to playtest them and perfect them.
Your opinion. It'll be disproven in a year, if I'm right. We'll see.
