Bay doesn't care about size, just look at Wheelie or Frenzy. The name 'Hound' suggests a guard, or a lapdog. To Bay, this means 'Guard = Big 'n' Strong.'
The truck in the back is an 1995-2000 Chevy WT pickup that definitely looks to have a lightbar on top. My guess would be firefighting vehicle.
So the rumor of Hound and Drift might be true. All that leaves is Galvatron and Lockdown. I'm not sure if the Dinobots are true. Edit: Also, I was looking at my Ratchet toys and both vehicle modes are technically Fire trucks. So would it sound like movie Ratchet if he changed to a Ambulance? Well of course since he's a medical officer. No offense, But I hope the Ambulance is a new Character, Specifically Prowl.
I can easily see someone going up to Bay and saying "So, I've looked into it and there's this whole 'Galvatron' thing." Then Bay says "He sounds cool! Let's make him! Is he a good guy or a bad guy?" because he assumes Galvatron is an entirely new character (Which I hope he would be in the movieverse.) Similarly with Lockdown, Bay was probably watching reruns of TFA on a saturday morning while eating cereal and wearing a onesie and was all like "Dayum, this guy's cool, I've gotta take notes!" He then flips open his notepad and doesn't take notes on any of Lockdown's actual personality, he just writes, "Hook hand = possible Space pirate."
So let's see, we've got 6 Autobots confirmed. Optimus Bumblebee Ambulance Military truck Bugatti Stingray And we still don't know anything about the Dinobots.
If that military truck turns out to be Bulkhead, it may just be a little harder for me to skip the movie toys like I had planned...
If that old looking truck is indeed Bulkhead that'll be awesome! If not well it can work as a Hound I guess.
I want that big thing to be Warpath. He'd be a better replacement for Ironhide than Bulkhead. But this is the movieverse, so it could be anyone.
Very exciting stuff. I think we're looking at Blurr (veyron) and maybe Springer (vette). Bay does not stick to paint schemes strictly though so the Vette could be any of the Autobot cars, or a new/reimagined character much like Blackout in TF 2007. Blurr tho...yeah the Veyron is basically Blurr incarnate. I like everything about prime except the overdone exhaust stacks. Seriously, that's a freaking amazing truck and HUGE, it's going to look epic in motion. Big military vehicle is almost undoubtedly Bulkhead. He's become a fan-favorite over the last two cartoon series. Hound could easily be a stand-in name. As for the continued rumors from multiple sources about the Dinobots making an appearance in the film....well, I can't really see them appearing in a chase-sequence on roads. They are big, ridiculously powerful bruisers. Even Bay can't screw that part up because the concept of ultra-powerful bots would appeal to him. I suspect that we will be waiting at least another month for any kind of confirmation of Dinobots. Possibly we could be waiting until the actual premier - if the concept of dinosaur based Transformers is retained, it's incredibly unlikely that we'll see anything of them because they'd have to be 100% CGI. The only hope we have of confirmation for Dinobots is on-set "parts" of them that the human characters have to interact with (like the mis-identified silverstreak in DotM that ended up being a random decepticon drone ship). Given that we saw nothing of Ravage or Lazerbeak except for in the finished film, I doubt we'll know for sure about the dinobots until a concrete reveal.
