It's not scientific, but I'd be plenty doubtful that the engine would last more than 100K miles with an aftermarket turbo kit on it, where it's quite usual for earlier generation, non-turbo rotaries to have lasted for at least 200k or more miles with regular maintenance. A reduction of engine life by half is something I'd call severe ...

 

Considering the power train and everything connected to is is the most expensive part of the car, and hooking a turbo into it will make every failure in that area suspect, I'd say that your warranty is pretty well void. Yes, it's true they cannot void your entire warranty, but they can certainly connect the dots on the important parts.