These look more like spin-offs then straight sequels. I'm not basing that off anything concrete, it's just that I don't see Kayako or Toshio anywhere in the trailers. I'm sad to hear Shimizu isn't directing, but I can't blame him for wanting to move on after 6 films (2 tv movies in Japan, 2 feature films in Japan, and the 2 American films.)
I'd actually be interested in some new storylines (not revolving around Kayako and Toshio.) No matter what, it's sure to be better than the Grudge 3! Yeesh that was a stinker =P