My understanding: SRD and OGL have nothing to do with WotC-produced modules. The SRD gives a subset of rules that can be referred to by anybody, and the OGL tells you how you can use them. It is my understanding that the OGL for 5e at least cannot be "pulled". It's built into the language of the contract. WotC modules are not produced under the SRD or the OGL. WotC owns the entire DnD IP and does not need this sort of arrangement. If you have bought a WotC product, you have bought it and it is yours. Although the digital age has ushered in a gray area where they can edit specific content, they are loathe to do this on a large scale. Example: If you bought Volo's Guide to Monsters, although it has been delisted, you still own it, physically or digitally. You just can't buy new copies (save for physical inventory still on shelves). As for the SRD Compendium, given the above assumptions, this would likely need to be a decision by Roll20, possibly tempered by agreements with WotC. In principle, there's nothing to keep the 5e SRD from being provided for free forever (like the 3.5 SRD). Licensing agreements may dictate otherwise.