I would like to first say that the entrance of Legion into the tabletop miniatures market will have an overall positive effect on gamers in general, more specifically I believe that the existence of a possible rival to the dominant 40k; at least dominant in terms of notability and player base. X-wing miniatures is the leader in overall sales, but 40k is the top dog in many other respects. Now the effect on gamers should come in the form of prices of both games, they are in the same niche, that being sci-fi miniatures ground combat, so they will compete whether they like it or not.
Now how does Legion affect 40k? 40k clearly has had an effect on Legion, if only in the fact that it was the first mega hit in the genre. Some tropes come inevitably from standing on the shoulders of giants. I do not mean in the sense that Legion is all that similar to 40k, but rather they occupy the same area in our brains. So what effect will Legion have on 40k? I believe that if the game proves to be balanced, affordable, and sustainable it will be a major competitor. And of course you will always have the Star Wars IP to deal with, and the GW haters that refuse to support GW and on and on. But by and large both games appeal to the same type of person.
Overall the effect each game has on each other, as well as others in the genre, will be felt over time. We as consumers can hope for more affordable toys, tighter rules, and more creative releases, expansions and organized play. Having more choice inevitably leads to better products that make your decisions as a consumer harder and this is a good thing. When one option is the only option you get inflated prices, and an overall worse experience. So what do you think?
Husband, gamer, coach, nerd among other things.