On an average metric, hell no, it's not a failure. I mean, I don't know how much Sony spent developing the game, but I doubt it'll come anywhere close to a commercial failure from a bottom line standpoint. But as Sony's biggest IP ever, it underperforming expectations is not a good thing.
I even think they are surprised for its good performance in europe.
Sony hasn't had a system seller since MGS4, and even that didn't help much (one month only)
They need to find THAT game. they did not need it in the ps2 era, but they need something both MS and Nintendo have and they don't. But that is something that usually comes unexpected, not that you can create a new great IP from scratch. Maybe they could push Uncharted, but i doubt it could reach that status.