Nothing is 100% but in general they have wanted 2500 hours for 777 so most likely go to 787.
I honestly don’t know why they treat the 787 as the beginner plane as it is even more complex than the 777- think it has to do with type of flying as 777 does more long haul and the 787 has more medium sectors.
there are lots of factors, including notice period required, etc....but it does seem that more experienced or those who already have experience on type are called first.