Yes, it's updated every few years. Most of the text remains the same, though, and the provisions that Castles* quoted appeared in the 2015 version (the numbering had changed but hte substance was the same word for word). On the face of it, we're bound by the provisions and there's not much chance we could quit the ECA and argue that its memorandum doesn't apply to us. It's a Swiss law document and we're going to be reliant on finding doctrines under Swiss law that allow us to wriggle out of it. You can be confident that we have absolutely top Swiss lawyers in our corner, and if ttere's a way, they'll find it.
* - It was Castles, not Conn.
I hope so and also think it's likely given the way he spoke, but as you say we just have to wait and see.