You could only cancel the contract if the leasor is in breach of contract. So if the contract called for delivery by a certain date and they missed that date, that would be a breach which would support your termination of the contract. Or even if there was no date certain specified, if the delivery is past any reasonable commercial expectation for when you'd get it--i.e. much later than if the norm for a commercial lease of this kind--then again, that could constitute a breach and justify termination. But if there is no breach, then the mere fact that you have no received the equipment yet would not let you terminate the lease or get out of the deal.