You have to be able to shoot it without knocking yourself on your butt. And I can see partial-augmentation within the decade if people put the money and such to it. Though I was thinking of a 25-40mm using a full power cannon cartridge for a sniper.
Four levels are available:
1. Uniform, gun. Not much else.
2. Add light body armor to #1, maybe more sense enhancement.
3. Heavier body armor, bigger gun, a more extensive set of sensors.
3. The armor contains partial augmentation to various degrees. Things such as "twenty-league boots," extensive sensors and information networking systems, perhaps a simple mechanism to allow a fairly large gun to be carried and used. Most of it would extend endurance, increase firepower, and threat detection. It's nowhere near the level of full power armor. Neural tie-on or another high-capacity interface may be used with this armor class.
4. Full augmentation. This includes armor that pretty much makes the person the equivalent of a light armored fighting vehicle, firepower to match, and sensors that make field conditions irrelavent. You might get as much as 1:10 strenth augmentation on top of carrying around your armor and such, a sealed suit, with self-contained air filtration and supply systems. Minor injuries would be taken care of by a special layer near the skin, plumbing included would allow an operator to be in the field in the armor for several weeks if he wanted to, with no need to get out to use the facilities or eat. The power supply could convievably last this long as well. Control would be achieved most likely with some sort of neural tie-in.
Beyond this, you get into true vehicles, not infantry.