So my local gw manager is loose lipped, or over-excited, and I've been asking things that the community have been asking. He's also pointed out some stuff they haven't. Bear in mind I'm paraphrasing.

1: How do we balance this?
Why bother?
2: What?
Seriously, it works. The scenarios where Nagash is the "underdog" vs 10 spearmen just isn't going to happen. Because empire guy isn't just going to say "oh, he has sudden death, better stop putting out models" empire guy is going to go "huh, just Nagash eh? I'll just keep getting out models until I think I can beat him, maybe even overwhelm him."
Then the undead player is going to pick the sudden death he thinks he has the most chance of hitting.
Sure it'll be a tough fight for one, or both, of them. But It'll be fun.
3. What about tournaments?
They can sort themselves out. They're clever guys, after all they've been re-balancing 8th this whole time because they thought it wasn't balanced. So how is this any different?
4. So what about army composition?
Take what you like, get bonuses for taking themed stuff. Simple no?
5. What's happening with Faction X?
Dunno, but we've seen images of flaming slayers smashing magma dragons so I'm guessing new toys and rules....
6. Will the new rules all be free?
As far as I know. They'll definitely come in the box with your toys; as for coming in a warscroll compendium, I'd imagine so, but i'm not 100%.
7. What about the lack of customisation in characters, absence of magic weapons etc?
Make up new ones.
8. Sorry?
Look, there's no points right? So why can't you just make something up?
9. Make up new ones?
Sure. I mean it's assetting with 9 infinite planes of existence, so whatever you imagine is out there somewhere.
I'm already making my own War scroll Compendium for Belakor's personal army from the realm of Shadows. I don't know if that's fluff accurate long term, but I love the idea so I'm doing it.
10. But what stops someone making up a super-monster and stomping everyone?
Social Darwinism. Seriously. How fun do you think a game against that'll be? None. And in a gaming club, or at a GW, word will soon spread and no-one will want to play you.
11. What else is coming out?
Dunno. Only thing I can say 100% is Stormcast with bows, because they're in the trailer. But I suspect more elemental / wind of magic themed stuff abounds, since the studio is now free to invent new species, units and whatever at a whim.
12. How long have they been planning this?
Remember Sigmar's Blood? (I didn't) It was a campaign book which was the prelude to End Times, so I'd hazard a guess at about 2-4 years. They plan things MASSIVELY ahead. Ages back someone came in excitedly telling me how they were adding a race of angels to 40k. Remember that rumor? (I did) I wonder if that was the first sighting. Wings, golden armour, round bases, makes sense right?
13: Should I re-base my models?
No need man. Don't bother unless you want to. I'm not going to for all of them, Just some.
14: How popular is it going to be?
Huge. I've sold more fantasy products this weekend than I made sales on my store birthday this year. And that was a big day.
15: What about existing fantasy players?
I hope they join in. A good chunk of my shop's regular guys already have. But those who don't want to can keep playing 8th, the I versions of all the rulebooks are still available because if we take them down then they get deleted from all apple accounts (he then went on to verbally blast apple for a while, he's not a fan for various reasons).

The conversation went on for a good while longer, we played the game too. It's good. Different but good. And I've still got every publication from 8th in physical form, so if I decide I don't want to play Age of Sigmar I don't have to.
But looking at how quickly the local crowd are adopting it, it may be hard to get a game of 8th.........