Can a Non-Thunderbolt device (like a mid 2010 iMac) connect to a Thunderbolt Display? I've been browsing different forums for this answer and the closest answer I could find was a post on this Stack Exchange. 

However this post is still a 'may be' it won't work and it targets the general question 'Non Thunderbolt to Thunderbolt ?' which I would understand to be negative.

My question is more on the display side, since the thunderbolt technology carries both a display signal as well a pci express signal, can a non-thunderbolt diplay with a simple display port still carry that signal to a thunderbolt cinema display ?

Thanks for your knowledge on that matter.
No, it cannot. That's the reason Apple is still selling the non-thunderbolt 27" display, for the devices like yours.

Source: Apple Online Store, where under system requirements it says:

System Requirements

Thunderbolt-enabled Mac computer, including MacBook Air, MacBook Pro, Mac mini, and iMac