Hi,
I haven't heard anything about a PlayMaker 2 release. Unity 5, as all major first release is really something I would strongly encourage not to rush with, especially for real world projects.
Always wait x.1 or x.2 before you actually use it for real, cause you won't be able to revert back if something doesn't work yet. Unity 3 and Unity 4 where in that position. I only started using 4 in production after 4.2 really...
Now if you are playing about and learning, then yes, embrace all the incredible stuff Unity 5 will offer as soon as you can!!
I would think that it's safe to get what you want know and not save for a possible new version of PlayMaker.
Bye,
Jean