With Hound confirmed as a Military Defense Vehicle for Transformers 4, the character's voice is sure to have a soldier/military like tone and best guess on who Michael Bay is casting for the character is on these guys
Jim Cummings (Tigger, Shocker, Nesis, Hondu)
Brian Bloom (Captain America, Black Mask)
Chris Hemsworth (Thor)
Adewale Akinnuoye-Agbaje (Heavy Duty)
Kevin Michael Richardson (Bulkhead, Roadblock)
and
Clancy Brown (Lex Luthor, Parallax, Taskmaster, Savage Opress)
Well for sure they are definately not doing Tom Kenny, Jess Harnell, Reno Wilson or anybody else that did a major character from the original trilogy and certainly not comedians.
Anyway be sure to choose who you think should voice Hound while filming on the fourth film resumes