We could be planning for the 15/16 season. Would not be surprised if a release clause of some sort has been negotiated in his new contract that is likely to be triggered next summer if certain aims are not met this season. Signing a long-term contract means nothing these days. In fact, it all seems rather ominous when a player that is in serious demand at a less fancied club signs a new deal, of late it often seems to suggest that a transfer out the club is looming. Two similar cases that spring to mind are Bale and now Suarez.
Hopefully i'm wrong and this doesn't pan out the same way.
But why would we sign Vorm now just so that we can keep him on the bench? He won't become a better player for his forced idleness. Besides which, he isn't good enough to be Hugo's replacement. If and when Hugo leaves, we will want a better keeper than Vorm to replace him as No. 1.
Far more likely that Vorm has been bought so that we have more of a like for like replacement if and when Hugo is injured.