But what about subliscensing? In what way would that be affected?
The short answer is "It's not clear." A slightly longer answer follows.
Here are the three key provisions of the OGL v 1.0a (at least in my view, in relation to your question; the emphasis has been added by me):
2. The License: This License applies to any Open Game Content that contains a notice indicating that the Open Game Content may only be Used under and in terms of this License. You must affix such a notice to any Open Game Content that you Use. No terms may be added to or subtracted from this License except as described by the License itself. No other terms or conditions may be applied to any Open Game Content distributed using this License.
3.Offer and Acceptance: By Using the Open Game Content You indicate Your acceptance of the terms of this License.
4. Grant and Consideration: In consideration for agreeing to use this License, the Contributors grant You a perpetual, worldwide, royalty-free, nonexclusive license with the exact terms of this License to Use, the Open Game Content.
The meaning of "Use/Used/Using" as it appears in these sections is extensively defined in section 1 of the licence, and includes a power to sub-license. I haven't seen any argument that it creates interpretive difficulties. The three italicised phrases, on the other hand, are interpretively more complicated in my view. Clearly they interact; but it's not entirely clear how they do.
To elaborate on that point: you accept the offer by using (some of) the OGC that is mentioned in section 2. What, then, is the subject-matter of the grant of licence in section 4? Here are three possibilities (there may be others; these are the three I've thought of):
* The licensed OGC is the OGC that you used in your work, thus accepting the contract as per section 2. (This interpretation treats the phrase "the Open Game Content" that occurs in section 4 as picking up the same phrase in section 3, where it is qualified by the "Using" that is the acceptance of the contract.)
* The licensed OGC is all the OGC that was in the work that, at the time you accepted the contract, contained the notice mentioned in section 2. (This interpretation treats the phrase "the Open Game Content" that occurs in section 4 as picking up the reference, in section 2, to "any Open Game Content that contains a notice . . . ", while confining the meaning of "contains a notice" to the moment of acceptance of the offer.)
* The licensed OGC is all the OGC that was in the work whose OGC you used in accepting the contract, so long as that work continues to contain the notice mentioned in section 2. (This interpretation is similar to the one just above, except that it does not confine the meaning of "contains a notice" in the same way, and rather treats that as a property of the OGC that must be ongoing, if the OGC is to continue to be licensed.)
On the first interpretation, once WotC revokes its offer then no new licenses are created, and everyone has a licence (which includes the power to sub-license) only in terms of their existing agreements. (Unless they enter into new agreements with other licensees who themselves have licences in respect of different OGC.)
On the second interpretation, everyone who has an existing licence with WotC at the time of revocation of the offer has a licence, including a power to sub-license, in respect of all the OGC in the SRD they drew from in entering into the licence.
On the third interpretation, when WotC revokes the offer then everyone's contracts remain on foot, but all the WotC OGC that is their subject-matter evaporates. So while in the abstract they retain a power to sub-license, as far as WotC's OGC is concerned there is nothing for that power to operate on. I imagine that this is WotC's favoured interpretation.
(A further possibility is that a party to the licence could accept, in the abstract, the third interpretation but further argue that WotC has a contractual obligation to maintain the notice in its SRD, because it has a contractual obligation not to cause the subject-matter of the licence to evaporate. I don't have a view as to how plausible this argument would be.)
As I've posted in other threads, if this matter is litigated and a 3PP is attempting to rely on their contractual entitlements to defend a claim for infringement of WotC's copyright, the 3PP will not want to rely solely on textual interpretation of the contract. They will want to lead evidence about the FAQs and other representations and conduct by WotC, both to support their arguments about interpretation and also perhaps to make out other arguments (eg that WotC is estopped from asserting that it can empty the power to sub-license of subject-matter).
But from the purely textual point of view, while I don't think my third interpretation is necessarily the best one, I don't think it's a hopeless one either. (For completeness: in an actual court case more work would be done by various parties to adduce considerations - from the general principles of contract law and copyright law, and from general understandings about commercial licensing practice, as well as closer reading of other relevant provisions of the contract itself - to argue for their favoured interpretation. I've only sketched some possible arguments.)