If neither Maajid Nawaz nor Tariq Ramadhan haven't left Islam then I doubt Hamza ever would. I always thought that Usama Hassan would become an apostate but that never transpired. I think that Tzortzis will develop his own theodicy and follow that whislt claiming that the burkha, stoning and Hell Fire have nothing to do with Islam.
Knowing Usama Hasan and his parents very well I don't think he will leave islam publicly whilst they are alive as they are devout wahhabis/salafis and he doesn't wanna hurt/upset them. From the way he speaks now he seems to be more Deistic/Pantheistic and refers to and talks alot about the beauty of nature/universe and god as a metaphor rather then the monotheistic abrahamic allah.
Interestingly 2 of usamas brothers have left England and shaved their beards and live completely non-religious lives. Everything which indicates they are probably apostates. Being raised in a fundamentalist family creates lots of infidels.