Thanks for the interview, Jon; it definitely gave me some things to think about.
1. Part of the thing with setting the PHB in stone, then moving on to other things, is that it leaves one wondering about how things will be divided. In their given example, I'd imagine that they would want to set how invisibility works in stone, then decide, "OK, so this class and that class can have access to the spell, and this creature and that one can use it as well, because we know how the spell works. Meanwhile, we know X and Y need another ability that allows them to stay hidden, but also attack while maintaining that concealment, so we need something else for them."
2.
. So you have things like legendary monsters, which are a special category of creature that is very powerful - their rules show up in the Monster Manual.
I wish you'd pressed him harder on this section about the MM, Jon. They promise a lot about providing the 'iconic monsters', but they always rattle off the same list of 'Beholder, Mind Flayer, Dragon'. What do they mean by that? Will there just be rules for one dragon in the basic set, will they do all the chromatics and save the metallics for the MM? Will the Mind Flayers be presented alongside the Aboleth, Elder Brains, and other 'iconic' abberations, or will they be all alone in the basic set (which leaves them both without part of their society, and sticking out if they are the only ones using psionic powers)?
Similarly, I remember an interesting post they made months back about how 'legendary monsters' would be tied with their lair; I think a black dragon was the example. Will the basic rules cover these situations, as I assume there will be at least one legendary monster incorporated there if they are going with the Tyranny of Dragons theme, or will there be a cut-rate dragon to which I'll have to add the legendary template to once I have the MM?
3.
We have a lot of information to draw from. Its been fourteen years since 3rd Edition came out.
And 7 Years since 4th Edition came out, but I guess we're keeping that locked in the attic. No discussion value here, but given how much effort they put into courting new players with 4th, I'm insulted they prefer to skip over what brought them in and act like nothing has happened in a decade and a half.
4.
Mearls: I don't want to go into too much detail because a lot of things are up in the air, but I will say that when 3rd Edition launched in 2000 there was this land rush mentality, and I think it makes sense from a business perspective. If you're a third party publisher you want to make sure you're the first to the market. Well, in their rush, you end up with people designing their adventure without the DMG. I was one of those guys. We want all the resources available, we want all the materials available, we want people to have been playing the game. We also want the audience to be informed.
Then why not make it available? Mearls clearly knows that delaying the DMG won't stop people from writing their own rules and adventures; instead, they'll do it with an incomplete knowledge of the game. WotC is fighting an uphill battle already against RPG players who love to mod things, powered by an internet culture that makes sharing trivial. If they want to reap profits from people and companies, they need something out there NOW; even a basic disclaimer like Apocalypse World has, where it encourages people to hack it for free, but to include the source they are hacking, and instructions to call Lumpley if they want to monetize.
In 6 months to a year, when WotC finishes their 'assessment', there will already be enough mods and adventures being shared and probably sold that no one will give a damn about the regulations (and there will undoubtedly be modules for mass combat and other things in the DMG that people prefer to the official versions, because they had to write them while waiting for WotC's version), and WotC will seem like the bad guys coming in to ruin their fun with their dumb restrictions.
5.
Mearls: We can't say anything there yet. But I will say that whenever there's an example in the DMG we used The Realms, and there's enough information there if people want to get started with a Realms campaign.
NOPE. Please tell me that WotC uses more than one example in that case. What's the point of having 30 years of history and half a dozen settings if all you tell new players about is the Realms, while the experienced players see nothing relating to the other settings and decide it's not worth it to play 5E when they aren't worth a nod in the fricken' DMG, and still have all the previous edition stuff for the non-Realms settings?
Honestly, as Mearls says, the Realms is a melting pot of everything from every corner of D&D, a choice that as far as I can tell was done solely to cram as much as possible into one setting. This leads to a weird beige effect, where nothing stands out; armies of magic golems from Renaissance-esque cities on the Sword Coast meet faux-medieval Egyptian and pseudo-Bronze Age Celts and nobody bats an eye. TELL THE PLAYERS about why warforged are a big deal in Eberron, or what the difference is between Realms vampires and Strahd in Ravenloft. The Realms is not so iconic that people will be happy with it alone, and not mentioning the other settings in the basic books (Mearls dodged the question about other setting books, so I assume they are at least a year out) will be seen as a slight.