The company never said anything about closing it down, but i'm pretty sure that it will happen. The process of streamlining will make the UI impossible to work at some point, so instead of patching it to make it work they are surely going to remove it completely.
Reddit released some numbers a year ago (warning: reddit link!). So it's another 4% of users using old.reddit (probably a huge overlap with 3PA users), but also 60% of moderators. I guess getting rid of it probably won't hurt them a lot.
I miss the times where every post was about how shitty reddit is. Now it's only original content. It's really going downhill fast.