As for me, I still hope Bryan Singer will. He should not have hanged the endings of the first two movies just like that, when he's not going for another sequel/s... I've learned a confirmation from 20th Century Fox that there's no script and no casting for the next X-Men movie has been done yet... but everything can be possible ... There are a lot of X-Men fans out there ... anywhere in the world ... so if the production wouldn't be able to come out another sequel ... it's not the fans lost anyway ... it's theirs.
So if Bryan Singer cannot direct the third X-Men film... it wouldn't be a reason not to have X3 ... He's not the only director and film-maker in the world, right?