Not liking Garrosh = Fine, not meta gaming
Plotting to take down Garrosh because you don't like him = Cool, not meta gaming
Claiming to know Garrosh is going to lead the world to ruin in the near future = Borderline meta gaming
Flat out "knowing" Garrosh "has to be put down" because "you know he'll be corrupted some day" = Retarded meta gaming.
Absolutely - I agree, we can't say "Garrosh is corrupted, Alliance and Horde are gonna besiege Orgrimmar before he screws up the whole world". Because we don't know that yet, and we won't until the siege actually begins on the live servers. But you can say "Garrosh will fall eventually" - no details, no predictions on how, who or why, just stating your opinion that he can't last at the rate he's going (and this is looking largely at his conduct in Wrath and Cataclysm, which will include the as-yet-unreleased event involving Theramore). People who dislike Garrosh have likely been doing so since he assumed power, anyway.
Edited by Saavedro on 3/21/2012 4:05 PM PDT