Clearly they are not, with the website hidden in the achievements on Steam, clearly showing a countdown for 11th April. We know it's bayo related from being derived from the Steam achievements, using the number associated with Bayonetta's watch, image from the first game etc. Regardless of what it is, it will be Bayo related, most likely Steam related. With all that in mind, chances are it is a port (at a big stretch a sequel). You can argue it isn't and that it's an anime or movie or some other thing, but Sega are most likely aware of what they are doing and the upset that would be caused to do this kind of joke towards a community that are actively chasing them for such a game. Highly unlikely that it isn't a game.