I kinda want to say go for full omake. If it's really planned out already, then for the most part writing/editing should be relatively fast. Also, if we only get half an omake with cliffhanger followed by chapter 50 and then the final half, it'll just mean we'll be stuck in cliffhanger hell even longer, considering that chapter 50 are still in the rough planning stages.
I would rather wait 2-3 weeks and have a full omake and another 2-3 for chapter 50, rather than have half the omake now, 2-3 for chapter 50 and then another 2-3 for the final half. Besides, the time that the cross-brain spends on writing the omake might allow them the time to finish planning 50.