The comment states Tesla performing well in the future is a given, a guarantee it'll exist in the future. We don't know what will happen in the future, I wouldn't say "x company existing in the future is a given".
It'll probably keep doing very well. It may have some sudden event happen that makes it stumble. I wouldn't even state that the future of transportation in 20-30 years is a given.
I wouldn't bet against Tesla in the next decade or so, but I wouldn't state its future performance is a given. You know, that whole "past performance does not guarantee future results" thing your broker keeps chanting. Unless you happen to have a crystal ball or some kind of time machine, in which case I'd like in on that.