The anime is going to do the split timeline thing that the games have been doing. It will be revealed that, anime-wise, there are two timelines (so far) and thus two Ash Ketchums. Timeline A Ash is the Ash we saw from OS to BW. Timeline B Ash is the Ash we've seen starting in XY to the present day. Each timeline has its own OS, AG, DP, BW, XY, and now SM. But the anime showed us the OS - BW of one universe (Universe A), and then switched to show the XY onward of the other universe (Universe B). Universe A's timeline still continued after the shift of focus, and Universe B's had already been going on before the shift, we just didn't see them. The 20th movie is going to be the origin story of Ash B, in that it will show us the OS of Universe B.
