Hello, I'm Shahid. Sorry to hear that you're having trouble with this but I'll do my best to help.
Just to clarify, TV displays Toshiba logo screen then switches Off, turns On again itself and shows logo screen and this cycle keeps going on, is this correct?
Your diagnosis seems correct and it seems firmware issue which is causing rebooting the TV repeatedly. Unfortunately FW update can't be reverse, I mean previous version FW can't be installed once newer version is installed so immediate remedy is to return the TV to have it replaced and some times Toshiba provide bug free firmware to stores and service centers prior to releasing it for public to cure the problem. Either the store will replace the TV or quickly update its firmware (with correct copy) to fix the problem. I'm sorry there is no other way around for an easy or quick fix to this issue. I hope these info will help. If you have any additional questions, feel free to ask. If you're satisfied, please rate me a 5-star at the top of your page. Thank you.