Do you think the rail gun will soon become common usage and replace old fashioned gun powder in military weapons?

What, no gunpowder?  Why, without gunpowder, the coyote will never get the roadrunner.

Old fashioned military weapons are almost obsolete.  There are new more sinister weapons on the horizon. 

We now use 'new-fashion' gunpowder. And no, I don't see a future in rail guns. Artillary is not used as much as it used to, with the advent of new rocketry. Tanks, of course are still needed for close-in battle.

 Gun-powder's been obsolete in artillery for a century and more, replaced by more propellants both more powerful and more practical. The huge naval guns of the first half of the 20C still used propellant external to the shell, but it was cordite or similar packed into cotton bags, not gunpowder. 

However, that is not really relevant because the question hides the stark truth that mere difference in propulsion does not stop the projectile or missile itself still being a lethal, destructive weapon.