If you root it with a method that doesn't do any damage to the firmware (some people write better programs than others), it won't have any effect on anything but apps that ask for root, because all it will do, other than install an app, is copy one single file to your system folder that's never used except by apps requesting root.
(If the method you use messes up files, anything can happen, up to and including bricking the phone.)
As far as waiting, if there's a rooting method for the current ROM in the phone, and you want root, root it. It's most likely going to be a while before someone finds an exploit to use in Lollipop to root it.
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