While all CGI would be awesome, it would be far too expensive. In the EW interview the direction said that he had to remove characters due to CGI modelling costs - and had to make hard decisions to even save Ravage, let alone his brethren. Likewise for Brawn and Arcee, who were only shown momentarily.
Animated is far far cheaper, but you get 'cartoony' cgi. Even then, its expensive, as we've seen with the REALLY short prime Wars trilogy animations. I wish they'd go for traditional cell painted animation, where you can have as many characters as you want without having to worry about CGI model development costs.
On the lookout for MISB Headmaster Highbrow, Takara or Hasbro. I'm sure I could make you a sweet deal!