My impression was that Airbus quite consciously decided to be a bit more conservative with the A350 after seeing all the problems Boeing had with the 787 switching to a zillion new technologies, all at once...
Airbus had also said that the Boeing was using too much carbon fibre on the 787, saying that it was too new a technology, but they ended up using more of it on the A350.
I bet all the newer airplanes will switch to bleedless engines in the near future.
