>>96468293
>Where does that come from and how reliable is it?
pure speculation and not at all.

People have theories based on the existing lore. I would say the three most popular are;

We know Grombrindal wants to bring the different Duardin together, and it's pretty damn likely that the Dispossessed are getting removed from Cities. So some people think GW will say that a lot of the Dispossessed joined up with the Magmaholds and Fyreslayers will get new units and characters with designs a little closer to classic Warhammer Dwarfs.

We know that Fyreslayers have started having more daughters than usual, it's been canon for ages that the women raise the Magmadroths, and the latest model Fyrelayers got had the first Fyreslayer women in it. So some people think that Fyreslayers will get a Valayaish expansion with a cavalry unit of ladies on teen Magmadroths and so on.

We know that the basic core infantry kit for Fyreslayers fucking sucks ass and is enough to turn people off the faction all by itself, and people who can get past that then face that the army has literally three fucking kits. So they think Fyreslayers will get a refresh/expansion that replaces the Berzerker kit and adds a couple more units, but doesn't mess with the overall aesthetic or expand the design space that much.

Those are all reasonable, they aren't mutually exclusive, and they are all completely made up out of people's brains. This teaser is the first actual solid information we have, and all we can learn from it is that Fyreslayers are getting at least one new kit, and it seems to draw more from the slightly tweaked design language of the Vulkyn Flameseekers than it does from the original 1st edition launch stuff. But is otherwise normal Fyreslayer.