You can't tell right now TBH. The one thing you can say is that St George and Melbourne will be there at seasons end, pushing for the premiership but even then someone else can win it.
Bulldogs, Tigers, Broncos are the other teams who will round off the top five IMO. They are all quality sides, and the former two are just a bit inconsistent ATM, while the Broncos are in a rich vein of form.
Despite, the Raiders languishing in last place, I can't see us in this form for too much longer. With the quality we have, this isn't characteristic, and with the likes of Dugan, Tongue and Campese returning in the coming weeks, it is only a matter of time before we click. I can see a 2010-esque situation for us, where we leave it late, finish 5-8, and put up a fight in the finals.
Manly, IMO, are showing they are a quality side and will be there or thereabouts in September, while you cannot write of the Roosters.
What we an take from previous years is that most teams can win it, as long as they aren't too far behind come around round 20.