Oh, they should know better by now. It's like the Scottish Play curse. They discussed a crossover back when the Doctor Who revival first aired, and Star Trek Enterprise got cancelled.

This time crossover talks put both shows on indefinite hiatus. You don't ever cross the streams, people. It's just too much space-time continuity to bring together in one event.

It could be the best or the worst thing that ever happend.

It would have been great