I agree with LeoRex, though I probably have far less knowledge to base an opinion on, but this is just my opinion.
Sd cards are, or will become more of, a bottleneck. I noticed a difference when I took mine out of a Note 3, so never put one back. Could be because of the app storage as said ^^, and now that I understand more how apps have to work with cards.
I don't believe in cloud services for the major part either.
I will keep a little there, documents, pdf's, some photos, important notes only I can decipher.
I'm old enough not to want to rely on ota data retrieval from someone's servers. I'm sure many are like me.
So I'm thinking now also the Note 5 will not have an sd slot. They have 6 months longer than the S6 to tool up and make 128gb phones more reasonably priced. There are probably other factors for sure, materials maybe, and even newer chip technology.
I don't think the majority wants to spend much more than $700 on a large volume flagship phone anymore, I could be wrong. Having a removable battery will give people confidence in it's longevity.
They could charge a premium for extra spec, finishes and a new Edge of course. So a Note 5 64gb as tier one, then a 128gb, and maybe a larger one?
It's transition time folks, cards are dying out on premium phones and 128 gb phones are increasing, but at a price just now.
I know this is a G4 forum, but I don't think many on the Samsung Note forums can face this yet.
If the G4 holds up well in practice over the next few months, LG should probably continue to take over the removables mantle in the near future.