I said it before but I'll say it again. Scalebound wasn't going to be successful or a system seller.
If you look at all of 13 of Microsoft's new IP this gen, only 4 of which could be considered huge titles, none of them did very well and are unlikely to get a sequel for this reason. And its not because those games were bad, though some of them had flaws, its because the game is on Xbox which is the underdog this generation.
Sunset Overdrive, which I still love to this day, sold pretty poorly, though exact figures are hard to lock down. The only new IP that Microsoft has released this generation that did well is Ori, and even then I don't think it did anywhere as well as the main three titles Microsoft are in love with at the moment. Honestly, even if Scalebound was a decent game, I doubt it would have sold well enough to get a sequel, especially when you consider that no one talked about it. Yes it may have some peoples most anticipated game on Xbox for 2017, but for the wider audience it just didn't seem to gain any traction.
I mean, this is all speculation because the game has been cancelled so we'll never actually know, but if an Insomniac title couldn't be successful on Xbox, what makes you think a Platinum game would have?
I'm not saying it deserved to be cancelled either, but I just don't think it would have done as well as a lot of people on here are making it seem.