I wonder if Mozilla plans on rewriting Firefox with Rust. Would that be too big of a task for Mozilla? They should also make the decision if they stick with Gecko or not at that point.
They are developing them in parallel.
Since rust is still an experimental project (the language isn't even finalized) it wouldn't make sense to replace firefox with it _now_.
So there is no "at that point" decision. Firefox+Gecko codebase is here to stay for a few years.
