In any case, the 1.4.7 packs released recently, and world updates seem to have gone without a hitch. (That said, the world generation did change somewhat - apatite veins are much larger but much rarer, and TC3 obsidian dungeons/totems have made an appearance). Still, as mentioned elsewhere, the launcher will warn you about an ID mismatch (or rather, show you a blank screen where it usually would) - I haven't had problems, but I'd back up my save, just in case.