I came across this interesting combination of Thunderbolt and eSATA bundle. Essentially it is a bridging solution for users sharing newer and older Macs, or those who will move to the new 2013 Mac Pro.
Mac Pro users might consider it for current use, setting aside the LaCie Thunderbolt to eSATA adapter for a future Mac Pro that lacks eSATA.
Current Thunderbolt-equipped Mac users might consider it in order to use a proven enclosure that can be moved between a current Mac Pro (eSATA) and a Thunderbolt equipped Mac: the Thunderbolt Mac keeps the LaCie adapter connected, and the dual-drive Mercury Elite Pro can move between it and the Mac Pro.
NOTE: most TB to eSATA solutions do not support Port Multiplication.