Looking at the documentation we are seeing that the crossbrowsertesting tool support various Operating systems and thus corresponding browsers as mentioned in the below link
https://crossbrow...
I'm really not expecting it unless they, somehow, develop a MacOS and Ubuntu version of TestComplete/TestExecute. Then, at least, they'll be able to run the tests on those OS versions. Likewise, until the technology changes when they will have something like a mobile version of TestExecute to run tests, I don't think it will happen.