The Samsung Galaxy Note 4 will sell well. All of the Note 2 users seem to want to upgrade to the Note 4. Personally, I want a closer to stock experience and do not care for all the Touchwiz addons, even for the s-pen. And the few things about the s-pen I like, I can replicate easily enough. That being said, I kind of love having the stylus, just to use as a pointing device, and also mainly for one specific game that pretty much needs it.
This is the perfect upgrade if you have a Note 2. The screen, processor and ram will make it easy for them.