@Fenrick: Rail guns could be made extremely silent and with low recoil, though. So I would expect to see some specialized weapons crop up here and there. But definitely not as widespread as conventional guns.

@NotMeNotYou: One of the biggest and most underrated advantages is the fact that you would have nonexplosive ammunition. While the weapon would still overheat, overheating wouldn't lead to cooking off, and for AFVs/ships, no risk of powder explosions.