There will be a Dead Space 4.
This whole thing about everyone wanting Dead Space to fail is really stupid. It's one of the most polished and well made game series around at the moment and not long ago there were reports that it had the highest pre-orders out of all of the Dead Space games and that sales were exceeding expectations.
I don't really get why people want Dead Space to fail considering how well it's made compared to the abortion that is Resident Evil 6.
So yeah, what has been "reported" seems more like tabloid bull**** to me.
EDIT: Also, more importantly, what the hell is everyone doing? The game has only been out for exactly ONE MONTH. Jeebus!