Yeah, but what code is going to be run?
Will it be the segwit tested code or some inferior variation?
It will be hopefully be SegWit activated via Bit 91 which makes SegWit2x and BIP141 (Core Segregated Witness) compatible.
BIP91 activates at an 80% hash threshold and rejects any non-SegWit signalling blocks and is signaled via bit 4 per the Silbert Accord.
Once BIP91 activates it functions like the USAF reject any blocks that do not signal support for SegWit through bit 1. Thus it is compatible with BIP148.
BIP141 is activated through the activation method defined by BIP9. This means that 95 percent of all blocks within a two-week period need to include a piece of data: bit 1
Following BIP91 the longest valid Bitcoin chain will consist of SegWit-signaling blocks only, and all regular BIP141 SegWit nodes will activate the protocol upgrade as the 95% threshold will be activated.
The only folks who would potentially not fall under the umbrella of BIP91 would be miners who opposed both Core SegWit and SegWit2x.
There is a good and detailed writeup in bitcoin magazine by Aaron van Wirdum.
BIP91: The SegWit Activation "Kludge" That Should Keep Bitcoin Whole
https://bitcoinmagazine.com/articles/bip91-segwit-activation-kludge-should-keep-bitcoin-whole/I had seen that Bitcoin magazine article soon after it released; however, your above description seems to bring some additional clarification to this matter, and maybe in the end, the segwit portion of the code is going to be fairly solid and implemented from the already tested versions.... and then we just have to wait for the next portion to see whether some uncertainties evolve from the rest of it, that involves the 2mb testing, implementation and whether there is sufficient consensus in regards to the hard forking of that...
Accordingly, we might be able to get through a few months before the next crisis hits, no? October-ish?