The reason we don't get a GPE Note 3 would be diminishing returns. The main selling point and attribute that the Note series has over the competition is its S Pen, which Samsung heavily implements into its UX. On barebones stock Android though, there would be limited functionality to an S Pen really. But I think that the Note series of devices have come a long way from being considered niche devices, and maybe we'll see Google doing something with the next Note based on just how popular it is.
But I sure am guessing they will launch a GPE of the GS5. I mean they did so with the GS4 so I don't see why they wouldn't. I hope the price is a bit lower this time though! $650 is a bit much for someone who buys subsidized phones all time time. Maybe around the $550 ballpark would be good.