I feel sorry for the people who have hung on to him to this point. There's no timetable on his return, and the last I heard is that the earliest he returns is a couple of weeks after the all-star break, so it's tough. Either you drop him now and he comes back in 3-4 weeks, or you hold on to him and only have him for maybe a month. It's totally up to you though.
In H2H leagues where you can sub in your bench regularly, then Arenas should not be owned unless you are sitting pretty at the top. In Roto, if you have a bench spot you don't need, then fine sit on him, but even then, he will not help you win a fantasy league this year in my opinion.
He might come back, shoot 37% on big volume with huge turnovers. Not something I want.