I am really hoping that they do switch to Zoom meetings permanently. Long may they continue. They may be helping Watchtower in the short term, but in the long term they will make Watchtower less relevant to everyday life.
Also, most people are there for the social aspect, even if they don’t admit it, or realise it. Zoom is a poor substitute for that, and adherents will find other connections over time, in place of that.
My prediction (just a guess) is that once the pandemic is well and truly under control, they may decide that KH meetings are to resume, but mid-week meetings will be by zoom, and the “preaching work” won’t include door-knocking.