For now, it's difficult to tell whether or not the claims will amount to more than just talk. There isn't an official case against Twitter at this stage. Also, Erdogan's views don't always mesh with those of Turkey's judges -- he believes the Constitutional Court is conducting "interference in politics" by upholding freedom of expression. When the politician has had success in banning YouTube, though, we wouldn't be quick to rule anything out.
[Image credit: Myrat, Wikipedia]