I think this discussion is somewhat useful but is almost certainly going to prove moot. The limiting constraint on when IETF is going to be able to resume in-person meetings will almost certainly be the point at which the host countries are willing to open their borders to visitors.
Note that even the UK has finally given in and imposed a 14 day quarantine for visitors. We can expect that approach to become universal as governments realize that a combination of social distancing and extensive contact tracing are (currently) the only viable strategies for avoiding the need for a renewed lockdown.
I can't see that happening until after the local lockdowns have been lifted a considerable time. Allowing international travel has the least impact as far as risk/reward is considered for the local population. It is not going to happen until after the shops and restaurants are open on a reasonably normal schedule.
What we might well end up having to consider is 'where can we meet?'. I see zero possibility of meeting in Madrid and almost no possibility of Bangkok. We may be lucky if we can meet in 2021.
