Hi,
Unity 5 being still a beta, it's dangerous to release a PlayMaker right now ( my personal opinion here, I do't know when 1.8 will go out).
I understand Unity is pushing for everyone to move to 5, It's a marketing strategy more than the best move you should do as a developer really... but I personally won't. The Main raison being moving sensitive project to x.0 in general is gambling with failure and frustration, it's always good to wait to the first patch or minor update like 5.1 for example, it was the same with Unity 4...
But I am confident that once Unity 5 is out for real, PlayMaker will release almost immediately an update, if not sooner.
Bye,
Jean