The question is, would they cancel the OGL? It's theirs, they could pull it if they wanted to, but I don't think it has hurt them, so why not update it and continue...?
As far as I understand it - and I'm not a lawyer, nor did I stay at a Holiday Inn Express last night - they can't really cancel the OGL. It is a perpetual license (section 4) and even if future versions are released that modify it, one can use previous versions, and anything distributed under any version of the license is still considered to be released under the license (section 9 - basically, their way of saying they can't redo the license more restrictively later, and immediately hose every other publisher).
However, they certainly could opt not to release 4e under the OGL.
(I suspect the wording/concepts of the rules of 4e would have to be significantly different than 3x to actually block publishers from the legal ability to make products mechanically compatible with 4e, since if the two versions were similar enough in terminology then a publisher could simply release 4e compatible products by using the OGL, which grants them the right to use open content. That would be something interesting to see.)