Earlier this year, Blizzard had a string of job postings that referred to an as yet unannounced FPS. There were not many details then and there are not now. The job posting is for a senior software engineer who specializes in gameplay and vehicles. As such, the only detail this posting offers is that the unannounced title will include the ability to drive around in vehicles.
It really is not much to go on, this new IP could be anything, if it really is a new IP. For all we know, this could be that Overwatch single player that was rumored around the time of Overwatch’s launch. Something that was definitely swept under the rug ever since, it is rather clear that Blizzard has every intention of keeping Overwatch an online multiplayer. The microtransactions alone are probably making them more than the game sales.
A remastered Diablo was rumored a little while back too, though Blizzard was quick to take down that evidence before it spread too far. However evidence about the title this software engineer post points toward an FPS, or at least a shooter in the more direct sense. Not the hack n’ slash of Diablo.
That said, Blizzard did mention that they have quite a few new IPs “incubating” in an earnings call back in August. At the time, Blizzard was most concerned with making sure that nothing was announced before it was absolutely ready. As the titles were to be “Blizzard-quality games” and anything that doesn’t meet those expectations would have to be worked on for a bit longer.
As that was only a few months ago, all of these projects are way too new and early in their development process. I reckon it will be another year or so before we hear more. At least not until Blizz-Con or E3, at which point the event will either be the same as it is every year, or the company will suddenly blow us away and we’ll have another great year for triple A games.