Compared to the G3?
If the LG G4 is the same size as the LG G3, then it's a clear upgrade.
LG has whipped out its latest Android 5.1 smartphone, the G4, and pledged that the handset will burst upon an astonished USA within the next few months. It will be available with a ceramic or real leather backplate. The new smartphone looks remarkably similar to its G3 predecessor. It's got a 5.5-inch QuadHD (1440p, 538dpi) …
Apparently they are making the 808 again. Or at least I saw a "new" one at a shop a year ago, not sure about the build quality though. I moved over to a plug-in, however you really, really, rrrrreally can't operate a 808 plug-in like the real thing when you're drunk (In it's end, those were the only times I pulled mine out).
I'm not sure this is worth an upgrade!
About the only thing which stands out on the list is the camera - though it'll be interesting to see how well this performs, given that image/video processing is one of the few things out there which can greatly benefit from speedy multi-core CPUs...