Generally speaking, a domain name registered before its trademark namesake existed can be protected against future infringement claims by them. A trademark aims to prevent likelihood of confusion, not necessarily grant one some claim over its domain namesake just because.
OTOH, it can become an issue if the domain holder did something to essentially acknowledge the trademark holder's existence, like putting ads reflecting products of the mark's competitors.
And as mentioned before, anyone can sue for anything. You just have to guard against such things as best as you can.