While the military has made plans for a type of powered armor to be used by infantry in the future, I'm afraid that we'll probably never see mechs of the "giant robot" variety (i.e. BattleMech.) They make for great fiction, but think about it: One arm on a mech would have many times the complexity of a modern high-tech tank, and would be many times the price. The only reason a large mech would ever be made is if it could do a job that other current military vehicles could not do. For the most part, mechs are just walking tanks. But we already have tanks, and adding legs to them wouldn't really be an improvement. Any small improvement to performance would be outweighed by the astronomical jump in cost. Also, the added complexity would mean added weight, which means shorter range, more frequent breakdowns, and added difficulty in field maintenance. (You should watch the Gasaraki anime series--now there's a pretty realistic view of what real mechs would be like, right down to the operational limits and maintenance problems, as well as an interesting take on Japanese mythology.)
If you want to read about the military applications of a powered suit, do a search for the Hardiman or Pitman projects. I think there was an article in Popular Mechanics on this subject. If I can find my copy, I'll give you the info.