the value of the block from 25 will become 12.5. So, the value will rise and possibly be doubled.
in a perfect world yes we are waiting for this but it's not automatically and probably in the first time we can't see any rise !
I think if the demand of bitcoin is not reduced. then for halving make the block is reduced of course the price will automatically increase but not doubled. The same happened if request or demand is rising? but if the demand price decreases. of course what happens is the price drop?