I would assume (IANAL!) that it would work similarly to software license upgrades. The IP created and licensed under version 1.0 would still be under version 1.0, and only IP created after 1.1 is released is affected, and then there must be some action on part of the small games company to agree to it.
I suspect it depends of course on the exact terms of license and what users of version 1.0 agreed to in terms of future binding.
Might be an interesting case with more than a little relevance for (US) software licenses
Wizards seems to think this will explicitly not be the case, and they can effectively force everyone to abide by the terms of a new license just by making one. Which maybe they can! But it seems like the right move might be to force them to try it.
I suspect it depends of course on the exact terms of license and what users of version 1.0 agreed to in terms of future binding.
Might be an interesting case with more than a little relevance for (US) software licenses