The main reason I think he can score a few more goals this season is that the team was so bad last season. Backstrom was cooked and so is Kuznetsov. Oshie played poorly until he took some time off and then he was very good down the stretch. Wilson played poorly all season. Aside from Carlson (who had a very nice season) the blue line wasn't good.
At the same time, they're playing a lot of younger guys like McMichael, Protas, and Lapierre. Those players are at an age where it's possible for them to take a nice step forward.
And in free agency/trades the Capitals rolled the dice. The team isn't going to be good or anything, but they might be better than last season. More importantly, the offense overall has an opportunity to improve.
Of course the flip side is he's old.