What Thunderbolt hard drives support daisychaining?
The drives with two thunderbolt ports are intended to work in a chain as opposed to the drives that only have one port. By necessity, these can only exist at the end of the chain.

Armed with this knowledge, you can always look at whatever models are for sale when you are considering a purchase and decide whether the added cost to have two ports outweighs the need to have a chainable device or buy a hub should one be eventually produced as a stand alone device.