I'm sure it will. Those discussions are happening right now among the Groovy core team members. I think, though, that the changes will largely be additions rather than changing anything we're already using. I have seen a default implementation for SAM (Single Abstract Method) classes, for example, that is consistent with how Java 8 will do things.
I believe that you can learn Groovy now, confident that when Java 8 comes out and Groovy grows to accommodate it, everything you learned will still work.