Bsyamato,
Even though we are all MS fans, I don't think 18m tall bipedal machines will become a reality. For one, since a typical mobile suit is 10x human size, the higher stresses would result in a bulkier form than a human's. I think the Zaku's weight was based on the assumption that it would weigh 10x10x10=1000 times a human's weight, which would be 75 tons for a 150 lb (68 kg) human. My guess is that a mobile suit would weigh a lot more, maybe 300-500 tons. A 1.5 MW (2,000 hp) generator would be totally inadequate to move such a heavy machine.
What started me thinking about this was a photo in B-Club magazine, where a Tiger I model in the same scale as a Dom was shown at the Dom's foot. The caption noted that the weight of the Tiger was essentially the same as the Dom's empty weight, but the Tiger was only the size of the Dom's foot. The Dom is supposedly made from steel-ceramic composite (real world Chobham armor?), so it's mass should be similar to the Tiger's.
And as anyone who has built a Perfect Grade kit will know, the movable bits are incredibly complicated, and a real MS would probably be more so. And before anyone chimes in to remind me that it is only science fiction, yes I know. I'm just here to buy the models and watch the shows; I don't live in the UC.
Personally, I think human-sized combat drones are more likely to become a reality. And non-humanoid ones are even more likely (robo-machine gun dog, armored giant cockroach, etc). And while powered suits are really cool, they don't address the vulnerability of the operator. So no Bubblegum Crisis hardsuits or Moto-Slaves.
But the UC origin of mobile suits as space construction machines is entirely possible. So coming full circle, maybe mobile suits might become a reality one day...
Oh darn, I've gone and confused myself now.