Hi Blitz Sprit,
Am a newbie with Macs but since no-one has answered your question I can give it a shot...
The TBD (Thunderbolt Display) has six ports on the lower left hand of the display when viewing from the rear.
They include: Three (3) USB 2.0 ports; One (1) Firewire 800; One (1) Thunderbolt; and One (1) Ethernet (CAT 5).
Your question is valid, if the TBD is connected to a MBP (MacBook Pro) for example, using the Thunderbolt connector from the display, can a Mini Display (MDP) to HDMI adaptor work on the back port? I say NO. Since the TBD initially starts with the MBP, for example, using a Thunderbolt connector and the Thunderbolt port on the back of the display would daisy chain ONLY other Thunderbolt devices. I am sure you've thought this out and could buy/borrow an adaptor and go to the Apple store and ask to try out your Blu Ray drive. The key that I think folks are thinking is that the Thunderbolt is backwards compatible. (Thunderbolt to MDP and vice versa).
What is great about the TBD is that the ports are like a dock station for your MBP or MBA, etc.
Back in the day these docks I used were called 'Port Replicators', which was great for docking a laptop (in my case a Toughbook) when working from the office and grabbing the laptop when going back out into the field. Sorry if I wasted your time with information you're already aware of...