Very very interesting discussion. Few more questions:

• What if at one point in time we have zero nodes supporting SegWit? What happens to all the SegWit transactions completed before that point? If old-style nodes do not read beyond 1 MB, does this mean that all those SegWit transactions will be like they never existed?
• If I understand right, Electrum currently supports only bech32 addresses and these are not backward compatible with old addresses. Is there any desktop wallet that allows you to create nested SegWit addresses?

Thanks a lot!