Copied from christoph’s Slack message (will be posted elsewhere shortly):
Trading with old accounts
If you don’t update to 1.2.0 you should be able to continue to trade with other peers that have version <1.2.0 as long as we don’t set the filter that 1.2.0+ is required for trading. This might happen ~3 days after the release. If arbitration cases occur during that time they can be handled by the arbitrators running 1.1.7. They will see the arbitration or mediation case also in 1.2.0, but to handle tickets they need to switch to version 1.1.7.
Updating existing offers
The reason for disabling all your open offers before updating to v1.2.0 is that during the process of updating the client if you don’t have your offers disabled there is a chance that an offer is taken and that would prevent you from updating. So in theory it is possible to update existing either live or disabled offers, but it should be done with disabled ones to prevent any unnecessary problems.
Updating during a trade
If one peer is updating after a trade was opened it will fail with an exception on certain message exchanges. From that point on the trade can’t be finished by the peers alone, as we don’t support the usecase of downgrading back to 1.1.7 again. Still the peers can chat with each other to find out why the exception is occurring. The only way to solve this is over a manual payout through the arbitrator (https://github.com/bisq-network/bisq-docs/blob/master/manual-dispute-payout.adoc).
Update during a dispute
Same as Updating during a trade completing the trade is only possible over a manual payout through the arbitrator.