Not much new content has been announced for 2019. We know Rebirth was pushed back to 2019 and Batman: Ninja Crossover has been announced. That's all we know so far.

When can we expect more 2019 announcements? Any more Crossovers or Rivals planned for next year?

You know, a Superman/Doomsday Rivals would be amazing. As would a Superman-themed Crossover. Just sayin'.