I think a lot depends on the definition and final form vs. function rationale. Transformers that can effectively 'stand' to leverage the ground for physical activities is fine. The space combat walker I included in the Artemis Frigate thread just below this would be a viable entity in any future. Where you have a machine designed for a specific task and optimized for this task. If it makes sense to have them on two legs fine, if it makes sense to have them skittering along on a hundred legs that's fine. Having big dogs that weigh a gazillion tons walking over ice, that have no effective field of fire, waste energy in inefficient movement methods that could be used for firepower, and are inherently unbalanced and unstable... now that's stretching things.