In order to quell speculation about his future, Arsenal plan to offer Arsène Wenger a contract extension adding two more years to his current deal at the end of this season. Wenger's current deal ends after next season, but the proposed extension would keep him in charge at Arsenal until 2019 – which would mean 23 years of Wenger at Arsenal, at least.
It kind of looks like recent form is causing this – of course, Arsenal has played well in general since losing to Olympiakos, winning four straight games including defeats of Manchester United and Bayern Munich at the Emirates Stadium. We're also tied with Manchester City on points atop the league, though goal differential has City in front in reality. But four good games isn't a good reason to commit two more years to a player, much less a manager, so it's doubtful that current form plays a big role in this.
Instead, we should probably read this as continued commitment to Wenger from the club. It's likely that even when things were "bad," this was planned. Stability is good.