Excluding unforeseen circumstances, there's no way shooting+post would take more than 15 months. Anything beyond that for a series like this is usually Additional photography or reshoots during post, which then need time for VFX too Publisher delays release to fit it into a slot where they have less stuff coming out. This is especially important…
It's moving along as briskly as the show itself, and I can't imagine anybody is genuinely excited to see Carol be lame and do absolutely nothing for 8+ hours again, in 2 years time when it maybe goes up on streaming.
I don't know what S2 will be, but this clearly isn't a show that's about the plot. I think if you're hoping it will do a 180 and be plot focused you will be disappointed.