Nope
"So I can arb between the price now and the price in the future."
No, you can't. When you do that you are taking a position. The arb implies that you have no overall position.
Depending on how exactly you are doing it you may speculate on outrights (the highest possible risk) or on time-spread (usually considered lesser risk but all depends on which particular markets you are talking about).
If you are talking about commodities you can use the strategy you mention to hedge your equal but opposite position in the physical goods but even then it is not an "arb". Normally such things are known as "contango plays" - when the forward curve is going up sufficiently steeply, you can buy your physical goods now, place them in storage and sell futures for the same quantity, say 3 months forward. If the contango is large enough to cover your financing and storage costs you will make money.
But even in that case there are still risks involved, higher or lower depending on whether the futures you used are deliverable or financially settled, whether your goods are of exactly the same quality, same location as the futures delivery basis etc etc.