@Brendanjones
The key thing is to avoid binary language. Saying the 1.5C goal is implausible, or we will certainly breach it, or cross it (or whatever) all sounds like we have (or we will) "cross a line". It sounds like game over, we lost. Think about how crossing the line in sports is equated with winning or losing.
Terms like "overshoot" imply a quantity to be managed, rather than a final state, especially if immediately followed by language that frames it that way.