LOL. Either he's trolling Copé or he's really deluded.
Is a Sarkozy return in 2017 really that inconceivable? He did, after all, get over 48% last year.
How is his popularity in the UMP?
The UMP base remains deeply and loyally Sarkozyst for now, transcending the Copeiste/Filloniste divide. So it's not impossible or inconceivable, the problem is that neither Copé nor even Fillon are too keen on the idea of passing their turn again in favour of Sarkozy, and we can count on Copé to do everything he can to sh**t on Sarkozy.
If Flanby continues to be a massive trainwreck, it is conceivable that Sarko could win a comeback despite being damaged goods and having a bunch of baggage. A poll recently said that 51% said Sarko would have done better than Flanby if he had been reelected; but then again McKayla Maroney would also do better. But after all, French people are politically schizophrenic and they love their hated presidents once they're out of office (though Sarko might be harder to love, since unlike Chirac he's not going away as a senile grandfather).