No, unless they licensed their work in a way that makes the new OGL the correct license (like the "GPLv2 or later" language some software projects chose).
WOTC only has the ability to change the license of IP they own, even retroactively. However, works based on WOTC IP which were legal under the OGLv1.0 may no longer be legal under the new terms, putting them in a legal gray area (they may be illegal to distribute, or they may still be legal to distribute but only because they were legal at the time they were created).
Creating new works based on the old IP that would have been legal under the OGLv1.0 would almost certainly not be legal if WOTC changes the license, though.
Note that section 9 of the OGL is an "or later" clause allowing Wizards to publish new authorized versions. (Wizards are now also claiming they can deauthorize versions which is much more wishful on their behalf)
WOTC only has the ability to change the license of IP they own, even retroactively. However, works based on WOTC IP which were legal under the OGLv1.0 may no longer be legal under the new terms, putting them in a legal gray area (they may be illegal to distribute, or they may still be legal to distribute but only because they were legal at the time they were created).
Creating new works based on the old IP that would have been legal under the OGLv1.0 would almost certainly not be legal if WOTC changes the license, though.