So, firstly, I can't think of any reason why you can't just make the bow (and the arrows) out of stronger materials to keep pace with your bionic arms. If we're talking about two or three or five times stronger than a normal human, you can just make the bow and the arrows out of stuff that has higher tensile strength to keep pace, and it should work just fine.
Obviously your arrows would go faster. If you're asking how MUCH faster, you have to start by defining exactly how strong your soldiers are.
I'm going to challenge you on 'sabot' rounds, because that is NOT a useful technology for a bow. Sabots allow you to shoot a smaller projectile from a large combustion chamber. With a bow, all your force comes from the mass of the arrow, so making it lighter AFTER you shoot it absolutely counterproductive.
EDIT: Since you specified a +100lb draw weight in the comments, that gives us some additional context. For reference, a compound bow usually tops out at 70 or 80lbs and shoots of draw weight, and that's for a big guy. Modern hunting crossbows go up to over 200lbs.
Some quick google searches indicate that a modern hunting bow will shoot at 400gr arrow at around 300fps, where top end crossbows will go up as high as 420fps.
So basically your soldiers would be getting crossbow energies and velocities out of a bow that can be fired much more rapidly and accurately, and with better penetration versus armor.
If you wanted to, you could probably make your soldier twice that strong and go up to 400lb draw weights without stressing the limits of what even modern technology is capable of in terms of the construction of the bows and the projectiles. The velocity seems to have diminishing returns so it doesn't seem likely that you'll ever get close to firearm muzzle velocities, but 500fps with a beefy projectile is going to have some incredible penetration and lethality against anything human sized, even in body armor.
EDIT THE SECOND: As a tactical note, I'll point out a couple other advantages those bows will provide. First: A faster, heavier arrow will suffer less deflection from wind or anything else (foliage, etc) that might reduce accuracy at mid-range. More importantly, there's a HUGE tactical benefit in the fact that a bow is (relatively) silent, and has no muzzle flash. If your hunters are being at all sneaky, it's going to be VERY difficult to spot them when they're shooting, and by the time you figure out where they probably shot at you from, they're not there anymore.