I hardly doubt the S5 Battery life (in theory it should be better, we will wait and see) is going to be worth the cost of an upgrade to most unless you have $$ just to waste/blow. An extra hour here and there?
I have a Galaxy Tab Pro 8.4 with the S800 and the battery life is mediocre at best, so it's not all chipset related.
I do admit the LG G2 is fantastic.
We're debating two different things. I disagreed with the statement that those with a 2013 flagship phone (excluding the G2) don't see a point in upgrading - the battery life improvement alone is non-trivial. When out and about on cellular network all day, I cannot get even 4 hours of on-screen time with my S4 (this with very few things syncing and all the gimmicks disabled). My G2 and Note 3 get 5 hours on-screen in worst case scenarios, and generally closer to 6 hours.
This is the difference between using the phone how you want all day vs having to be judicious. Going over 6 hours on-screen a day I think is the point of diminishing returns as even from 7am to midnight, there's only so much time you can be looking at your phone.
Now, whether this is worth the cost of an upgrade (say $300 after selling your phone) is something else all together. For some, no. For others who spend that much on gadgets regularly, sure.
And sure it's not all chipset related, but there has been a clear improvement in battery usage from the S600 to the S800. That combined with a larger battery and other improvements (like the Lucid power saving profiles), I'm guessing we'll see something in between the S4 and G2, but closer to the G2.
tl;dr - there will be nontrivial improvements, whether they're worth the cost to you is not what I was arguing.