I sent an e-mail to Attakus team asking for some info about series 4 and I've received this reply:
"Hello !!
First Star Wars statues to be released: Grevious, Wicket & Tusken Rayder, September, October, no prices available yet.
Here's a link to our forum where you will find the prototype pictures of these statues:
http://forum.america.attakus.com/viewforum.php?f=8
Best regards
Diego Arnedo
Attakus Team"
I just want to share the info.