Here is some documentation.
http://support.apple.com/kb/HT5219?viewlocale=en_US&locale=en_US#dispnum
Specifically this, noting the footnotes. I've done some editing for readability:
How many Apple Thunderbolt Displays can I use with my Mac in OS X?
The table below indicates how many Thunderbolt displays can be connected to Thunderbolt-capable Mac computers in OS X.
Computer Maximum number of connected displays
Thunderbolt-capable Macs with only Intel HD Graphics 3000 integrated graphics can support one connected Apple Thunderbolt Display (27-inch):
MacBook Air (Mid 2011),
MacBook Pro (13-inch, Early 2011) and (13-inch, Late 2011),
Mac mini (Mid 2011), 2.3 GHz,
Mac mini with Lion Server (Mid 2011)
Thunderbolt-capable Macs that can support up to two connected Apple Thunderbolt Displays.
MacBook Pro (Retina, Mid 2012),
MacBook Pro (13-inch, Mid 2012),
MacBook Pro (15-inch and 17-inch, Early 2011) and later,
MacBook Air (Mid 2012),
iMac (Mid 2011),
Mac mini (Mid 2011), 2.5 GHz,
Note: The F8 key does not work when using Windows with a USB keyboard connected to an Apple Thunderbolt Display (27-inch).
1 You can connect a second Apple Thunderbolt Display (27-inch) to a MacBook Pro (13-inch, Early 2011) and (13-inch, Late 2011), but the built-in display on the MacBook Pro will go dark. This is expected behavior.
2 iMac (27-inch, Mid 2011) with two Thunderbolt ports supports a total of two Thunderbolt displays regardless of which Thunderbolt port each display is connected to.
3 Mac mini with AMD graphics can support an HDMI compatible device on its HDMI port when using two Thunderbolt displays.
4 MacBook Pro (Retina, Mid 2012) can support an HDMI-compatible device on its HDMI port while also using two Thunderbolt displays.
And here's an OWC article with an image showing a MacBook Pro with Retina that has three attached displays plus the built-in.
http://blog.macsales.com/14241-macbook-pro-15-with-retina-display-can-run-3-external-displays
I took my December 2014 Retina MacBook Pro into the Apple Store with the problem but they couldn't reproduce it in the store and asked that I come back with a device that demonstrates the problem. That evening, I spent some time at the office and at home trying to reproduce the problem while capturing it on video. I was able to reproduce it with a DAS Keyboard, Logitech Mouse, a Dell Keyboard and a Dell Mouse (via USB port).
I brought the system and two devices into the store but I started out offering to show them one of the videos. The Genius Bar Tech watched one and agreed to replace the logic board. It's at the Apple Store now and I expect to get it back sometime next week. This problem is most intermittent - it took a fair number of tries to get it to show up these couple of times.
https://www.youtube.com/watch?v=FmQPl2DaUrc
https://www.youtube.com/watch?v=XxG0loDpes8
EDIT:
I got my system back with the new logic board and the problem is still there. I think that I'm just going to live with it as it's typically cleared up with a plug/unplug and reboot. If it becomes a hassle, then I'll get a port hub, either Thunderbolt or USB 3.0.
It appears that this is a problem in currently shipping product. Hopefully they will eventually fix it.
Best Answer
Thunderbolt 2 is backward compatible with Thunderbolt 1. So it should work no problem unless the product manufacturer says otherwise. Thought you only gets half the speed since the port on the computer only have Thunderbolt 1.