Brian Clevinger is a good choice.
If the Skybound rumors turn out to be turn then MAYBE Robert Kirkman will tackle it...but if so, probably only for a mini-series or two before handing it off to someone else. He might have some childhood love of Transformers and want to do the book for a bit. But, he's a busy guy and has his own books to write and TV shows to oversee and companies to run.
Joe Keatinge is a possibility. He did the Tech Jacket series, which tied into Kirkman's Invincible comics. He's not bad. He's done the Glory reboot and Shutter, which were both solid books.
Jim Zub would be a interesting choice, I think. He's mostly done Dungeons and Dragons stuff, but he's shown to be able to work off a franchise's lore. And work with a medium-size cast of characters. I think he'd be able to do interesting things. He's done Skullkickers, Samurai Jack, Pathfinder, Conan, Avengers, Stone Star, and the MANY D&D Baldur's Gate miniseries.
Joshua Williamson would be another interesting choice. I really like a lot of his creator owned stuff, like Nailbiter and Birthright. He brings a horror edge to things in his creator-owned stuff. I DO think his licensed stuff is a little weaker, though. His Flash run is perfectly solid, but doesn't really stand out. And Dark Crisis kind of just feels like him playing with action figures. So, he could either be a really good choice that could bring some new energy to Transformers...or it could just end up being a "solid enough" comic.
John Arcudi could happen. He's done a lot of little things. Doom Patrol. Rumble. BPRD/Hellboy. Aquaman. Conan. Thunderbolts. He's a little gritter. I could see him doing something with the Wreckers.
Ryan Parrott would be a good choice. He's most notably done some of the Power Rangers comics. But, he's also done Rogue Sun, which I like. And he's worked on Star Trek comics, too, so he's no stranger to doing licensed work.
Kyle Higgins is less likely, but not impossible I guess. He's just busy building his own little universe with all the Radiant Black books. He's done the Ultraman comics for Marvel and Power Rangers, too. Along with Batman Beyond and Nightwing. I just think he might be too busy with other stuff, at least right now.
Kieron Gillen is pretty unlikely. He has done a run on Iron Man, though, so he has some experience with robots. He's also done Once and Future, Darth Vader, Journey into Mystery, Die, Eternals, and Warhammer 40K. He's really good...but I'm not sure if he's one who sticks pretty close to Marvel, mostly.
Al Ewing is...highly unlikely, but a interesting idea. He's a writer who brings some interesting ideas to the table. He might be able to bring a interesting angle to the franchise. He's done Immortal Hulk, Ultimates, Defenders, Loki, and is currently doing a run on Venom. He has been sticking mostly to Marvel, though.
Jonathan Hickman is VERY unlikely but I, personally, would find it VERY interesting. He always brings interesting high concepts to a franchise. His runs on Fantastic Four, Avengers, and X-Men are all-time greats, in my eyes. And some of his creator-owned stuff, like Manahattan Projects, is similarly captivating. Sometimes he's inscrutable, like in East of West, but he's always interesting. And he needs SOMETHING now that he left X-Men (*SIGH*). Plus, Hickman's love of graphs and charts would go GREAT with giant robots! It's a match made in heaven!
But, there's every possibility that it'll be someone new we've never heard much from before. It's really hard to say.