AC vs DC voltage is much like Disc vs Drum brakes, there are benefits and drawbacks to both, I think we will see the return of drum brakes before we see a DC distribution system, transmission yes.
The advantage of AC has always been that it is easy to change the voltage up and down with a transformer; DC requires more equipment and some losses to convert.
That being said, transferring AC power between separate grids requires making sure the phase of the power transmitted matches from the two grids (so that the power from the two grids doesn't cancel or ring), which is difficult and expensive. This is not a problem for DC, so DC lines are used in cases such as where power is transferred from another grid to increase the capacity of an existing grid, or between countries that use different frequency power.
Capacitance between the AC phases (usually 3 phases are transmitted at once over a line) or between the line and the surrounding soil or water causes losses that are not a problem with DC. Therefore, undersea high voltage lines tend to be DC.
Overall line loss is also lower per 1,000 km, so very long distance transmission lines sometimes use DC.