GSP’s last fight was a controversial bout against Johny Hendricks at UFC 167. Despite it appearing to many that Hendricks had won the fight, the judge’s awarded the split-decision victory to St. Pierre. It was his 9th straight welterweight title defence.
The fight is controversial both for the judge’s decision, but also for Hendrick’s refusal to take part in advanced drug testing that GSP offered to pay for. Although Hendricks initially agreed to the advanced testing, he pulled out when logistics were being arranged. GSP has stated since then that the prevalence of PEDs in MMA played a role in his decision to take a break from the sport.
Listen to Georges St. Pierre talk about the UFC offering him a fight with Michael Bisping:

Those around Georges say that he is looking for big-money fights and not necessarily championships, although he expressed an interest in possibly fighting current welterweight champion Tyron Woodley. It appears however, that Dana White wishes to arrange a title fight between Woodley and Stephen “Wonderboy” Thompson next however.
By the time GSP steps in the Octagon at UFC 206 in Toronto, it will have been over 3 years since his last fight. While that time away from the octagon has never served a fighter well, GSP is a different caliber of athlete than most. It is entirely likely by this time next year we will once again be talking about Georges St. Pierre as one of the top pound-for-pound fighters in the world.