Miniature wargaming is an industry in which the quality of a product (gaming system) is looser linked to its popularity than you see in most other markets because of its heavy reliance on
network effects. If in a local area two people play a system it will provide some utility to both but they will tire of only being able to play each other after a while. If 30 people in the local area play a system, every player has a myriad of different opponents (both in terms of people and armies) to play, which will be much more fun. Essentially, the more people that play the system, the more utility each individual gains by playing it. It is the same reason that even if a new social media network is technically better than Facebook, Facebook will probably retain supremacy.
While I'm not sure that there is any hard and fast data about the popularity of AoS vs 9th vs KoW, many reports seem to reflect what would be expected in a market with network effects as the uptake of each seems to have been been highly regional. In the USA, KoW seems to be the dominant game (although there are pockets of the others); in the UK I think AoS is slightly ahead and will benefit from GW's concerted efforts to make it succeed; the rest of Europe seems to be edging towards 9th. This is probably in part due to a heavy reliance on Games Workshop stores in the UK (gunning for AoS) whereas the US has a more varied craft store market that helps the better game succeed (KoW), and no one seems to concentrate on Europe so they have just continued with same old, same old (9th). There is still some room to manoeuvre at the moment as the market has not yet settled after the destruction of the Old World. However, whichever systems do start to edge in front in each area, it will get progressively harder to alter the dominant system as new players will inevitably play the game that most other people in their area do.
One possibility that seems plausible in the UK market (which will remain heavily influenced by GW) is that AoS becomes a gateway game for KoW. I have started seeing this and can perfectly understand it - Uncle Atom (Tabletop Minions) explains
why AoS is such a good gateway game, and as players progress on to better-developed systems KoW's popularity in the UK compared to 9th, as well as the fact that it is considerably more fun to play, could make it the 'go to' game once people want something a little more substantial. Whatever happens, Mantic seem to be doing well at the moment as Clash of Kings (the main annual KoW tournament) has gone from 36 players in 2015 to 80 last year and will have 120 this year. I know KoW's main criticism is that it might be too heavily focused on tournament play, but if it can feed off AoS then that position is entirely sustainable in the longer term. Here's to hoping!
Are you being serious?