I think it is not.
The tagline "Horror Lurks Within" has got people thinking Morph, and this is possible, but it was brought back only a few years ago in Time Spiral and I'm not sure it deserves a threepeat this soon.
But I did abruptly think of one card that might fit that slogan:
What if this is the Transfigure block? Just think of it - a secret legion of shapeshifting monstrosities infiltrate an entire plane, so you never know what form they're going to take next! That's what I call "horror lurking within".
Shadowmoor and New Phyrexia both did a good job of being "horror world" sets, but we haven't seen something that really hits the archetype of "body horror". New Phyrexia is just close enough that this could be a good segue. And hey, Fleshwrither looks not entirely dissimilar to the Eldrazi, so maybe they're behind the Transfigure invasion - or maybe Phyrexia is - OR BOTH!