Unfortunately, only time will tell. AFAIK, the present plan doesn't call for ZScript deprecation for a jolly long time. I'm mostly uncertain if it's even plausible to do such a major rewrite, and not break the universe in the process. We have so many compatibility rules as things stand, that implementing all of them in a rewrite is simply...madness.
The hope is that when ZC3 is a thing, and a new language is implemented, quests with ZASM tables will still work, most of the time.
It won't be the 'next version' though. Somewhere down the line, certainly, but not next. That, and I may be mad enough to continue supporting 2.xx stuff after it is officially deprecated. We'll see in a few years how much steam I've left.