If they drop shunning I think they’ll do it gradually in a way that doesn’t involve any great climbdown. They’ll just suggest that a little more contact with disfellowshipped people is reasonable, then a bit later talk about “reaching out” to people who’ve left the faith for whatever reason, and before you know it the days of hard shunning will be over. The change might then be papered over by a mixture of saying the light/truth gets brighter/clearer, Jehovah is merciful, it’s a new “provision”, and so on, plus downplaying how harsh shunning used to be in the past. That’s how they could get radical change on shunning over a period of a decade or so without having to effect a big climbdown or explicitly admit their previous policy was wrong or inhumane. I don’t think they need any outside advice on how to go about that, because they’ve managed similar changes on their own, for example when they watered down their opposition to ‘alternative service’ in the 1990s, which was a huge change for those affected but didn’t involve any mea culpa on the part of the GB.
I don’t think they’d tie in any change with jubilees or cities of refuge or anything like that because 1) they have abandoned the typology involved in such applications of scripture in recent years and 2) an explicit amnesty could imply a fault with the previous practice when they are not in the habit of admitting fault and don’t find it necessary when making even big changes anyway.