Raimi told ShockTillYouDrop.com last fall that he was trying to crack a story for a script rooted in the horror genre. Maybe this is what he was hinting at?
Now, you might think he was saying this in jest, but I don't think so. Raimi understands the fanbase the series has and he's very aware that there is a desire to see a fourth part. So, I don't think he's being a tease.
Of course, we'll see what transpires. Naturally, the next questions that will arise will be: How does Ash factor into all of this? Will Bruce Campbell be back? And so on...