Linear Time Invariant System Causality
The only possible way that I can conceive of that system being non-causal is if y[n] is not the output of the system. 

As long as the forward time dependency is finite, it is always possible to add delay to the system to write it as a causal recurrence form. 

That is, just multiplying the z-transform by \$z^{-N}\$ would yield a causal system. 

But if y[n] is the output, it is causal.