The next phase is the "Limit phase".  In the limit phase voting for a lower block reward has the effect reducing the max money supply from 128M to something smaller.

The max vote is still 1024. The duration of the limit phase is in the number of blocks.

So if the voted block reward is 512, then for each block mined 512 coins are effectively lost from the network forever and the total money supply decreases.  (The coins that are "lost" are the 512 that could have been mined if the block reward was the maximum 1024.)