The iPad Pro is a niche product, to be certain, but I don't think Apple expects anything more from it than that. I know a lot of artists and graphic designers and they are all (myself included) absolutely champing at the bit to get their hands on one. Wacom may currently be the best-in-class for pressure-sensitive stylus input, but they don't set the bar particularly high. If Apple gets this right, they're going to put a nasty dent in Wacom's business. If Astropad works as advertised, and the pencil is as good as everyone says, then I think there's a real possibility I may sell my Cintiq.
(FWIW, I already have a Surface Pro 3, which I think is pretty poor. It's not laptoppy enough to replace my laptop, but not tabletty enough to sit in a workflow gap between my laptop and phone. The non-Wacom pen that ships with the Pro 3 really isn't up to scratch for artwork, either.)
This is the one thing I hope the Apple pencil does, is knock Wacom around a bit and make them more innovative. MS is trying to do that with N trig, but they aren't quite there yet. The Vaio I own uses the same Ntrig digitizer as the SP4, and it still has that annoying diagonal jitter issue. More competition in the stylus/ digitizer market is a good thing.
That Astropad app looks very interesting, and could convert a iPad Pro into a Cintiq if it works well.