I’m lucky that the run on 4e has been a really good one and we’ve had circa 25+ products. I have enough to set me up for the next 10 years of gaming. But I really do worry for some of the spin offs.
WFRP4e (2018): 31 distinct physical products/books (not counting special editions, etc.) (WFRP2e had 29 physical products)
Soulbound (2020): 15 distinct physical products/books (not counting special editions, etc.)
With the big difference being that WFRP had 3 editions and 32 years of content to directly mine from, many of those 31 WFRP4e books are remakes of existing adventures. A lot of the content is direct translation of what came before it (1e/2e).
Soulbound is based on Age of Simar (2018) miniatures game, which was essentially a very different world as WFB (1983). WFRP4e just had a far easier time to produce material the Soulbound has, they have to invent the wheel, from what incoherent slop GW has been producing for AoS.
It also doesn't help that WFB has a baked in fanbase, AoS a whole lot less so. And that for the longest time people were playing WFRP2e and not really WFRP3e, which was a whole different beast.
Also keep in mind that Wrath & Glory was made by Uliesses Spiele in 2018 (the same time C7 started with WFRP4e), but they F-ed up. The 40k license went to C7 (2019) and they had to rewrite/redesign the whole game, which was entirely unplanned. Still it has 13 distinct physical products/books (not counting special editions, etc.)
The original Dark Heresy (2008) 1e only had 15-20 physical products (depending on how you count, there was a boxed set that combined three adventures for example) in 5 years. 2e only had 6 products in 2 years.
Rogue Trader (2009) 16 physical products in 4 years.
Deathwatch (2010) 14 physical products in 4 years.
Black Crusade (2011) 8 physical products in 2 years.
Only War (2012) 8 physical products in 2 years.
Imperium Maledictum (2023) 6 physical products in 2 years.
And Cubicle 7 is a whole lot better at supporting their lines with digital products the FFG ever was...
I suspect that if I ever were to run a 40k campaign I would turn to the old FFG (and Black Industries) versions of the games rather then going with W&G or IM versions...