Resale prices are still pretty volatile because there's little information on the long-term reliability of the bikes. They won't have many of the issues that gas bikes run into as they age, but may have other issues specific to electric powertrains or Zero's particular implementation.
Zero is probably too small to offer a leasing arrangement .. and leases are rather uncommon in the bike world anyhow.
Zero offers a 2 year warranty standard, and Brammo recently matched that warranty length. That's longer than most Japanese bikes (1 year typically) but matched or exceeded by some European bikes (Ducati, 2 years; BMW, 3 years). I think an optional extended warranty, including battery durability a la Nissan would go a very long way towards easing some of the resale volatility and ensuring a new buyer can buy with confidence.
In any case, buying any vehicle new and selling after one year of ownership will result in taking a bit of a bath. Zero is no exception.