Eh... when something goes from version 1.0a to 1.1, it seems like an update to the parent item.
In this case there is no "parent item", and nothing is "going" from version 1.0a to 1.1.
These are just names given to privately-drafted instruments. WotC could call the instrument whatever it wants.
The issue of whether or not it is a "version" within the meaning of section 9 of the OGL v 1.0/1.0a will depend on its terms. Given what WotC has said in its press release, and given the leak, I think it is pretty clear that v 1.1 is not an "update" to anything. It is a distinct licence that will not be part of the OGL v 1.0/1.0a ecosystem.
I mean, if I published a piece of software called Organized Gaming Library and released v1.0a, and some time -- perhaps a long time, I'm a busy person -- related Organized Gaming Library v1.1, people could reasonably expect this to be an update to the same program.
I'll take your word for that. I don't know much about software. I'm talking about contract law.
The OGL contains no provision for its own updating. Section 9 is not such a provision (despite using the word "update"). What it permits is (i) for WotC to issue new licences which (ii) licensees are free to pick and choose from when they use OGC.
Now, if I published Organized Gaming Library v1.0a some time ago and then released Organized Gaming Library v1.1 and said it's not an upgrade, but you can either switch to and continue organizing your gaming library or stop organizing your gaming library, but either way cannot continue using the old version... I think my user base might be some combination of confused, upset, and angry. Even if I was entirely clear in my notice that this... not update, this new version, would do that.
Sure, OK? Again, I have no expertise in market responses to software variations. I will say that when my computer updated itself form Windows 8 to Windows 10 (? or something like that - I'm remembering an event from years ago) I didn't get angry, even though it seemed to me that what had happened was a replacement of my Windows version which meant I could no longer use the old version.
But anyway, we're not talking here about software naming and marketing practices. We're talking about contract law.
I believe this was the intent and what those using the OGL understand.
Which is why, I would think, WotC declared in v1.1 that v1.0a is 'unauthorized'.
My understanding of 'authorized' in this context is along the lines of 'issued by an entity with the authority to do so. That is, you or I can't issue an update to OGL because I'm not with the right organization, and the janitor at WotC can't because he doesn't have the authority in the organization, etc. It can only be done by or at the direction of an appropriate officer of WotC, sort of thing. On the other hand, WotC seems to be saying either that OGL v1.0a is not authorized for use with this content (least bad interpretation) or 'OGL v1.0a is no longer a valid license' (much more bad).
Until the whole text of v 1.1 is seen, we can't know what role "authorisation" plays under that licence, and hence what it means for that licence to state that OGL v 1.0/1.0a is not an authorised licence agreement. (I doubt very much that the formal contractual text will use the phrase "no longer".)
You say "WotC seems to be saying either that OGL v1.0a is not authorized for use with this content (least bad interpretation) or 'OGL v1.0a is no longer a valid license' (much more bad)", but there's no reason I can see to think that they are saying either of those things.
WotC has given an outline of the content of their draft OGL v 1.1, and have indicated that under that licence, v 1.0/1.0a will not be an authorised licence. So the most obvious conjecture, I think, is that the OGL v 1.1 is going to be a (quasi-)open copyright licence, and hence will have a provision similar to section 9 of OGL v 1.0/1.0a, and furthermore will expressly state that v 1.0/1.0a is not an authorised version of the licence for the purposes of that provision.
Whether or not that is a bad thing is not a legal question, and I express no opinion on it. My only point is that it is neither of the alternatives that you are putting forward.