A niche product isn't going to hurt Sony's momentum. As someone pointed out in another thread, people who wait to jump into a console gen are doing so because of price. A $199-$249 PS4 S is going to appeal to them much more than a $449-$499 Xbox will. If they are interested in a more powerful box, one that's a little weaker than the Scorpio, but is $100-$200 cheaper is going to appeal to them much more. As it is, the Pro and the Scorpio will be selling mostly to early adopters who want an upgrade. At least until the prices come down, which will be happening for the Pro later this year.
It also helps that Sony is known for its vast library filled with variety, including high quality 1st party games. Where the XBO is missing out on a lot of games this gen, especially from Japanese devs.
