Yes, I own the 5S and will be upgrading to the 6+ with either 64 or 128GB capacity. (Probably the latter.) I have been waiting an awfully long time for the Apple phablet and I can see myself using it much more than the 5S. I currently use the 5S for news, messaging, twitter and general apps and things but I swap to the iPad Air for games and proper reading. However, with the 6+, I will no longer have to do this because the screen is just so big and gorgeous. I really question the need for my iPad Air at all.
And, actually, I recently bought the 13" rMBP and that has displaced my iPad Air as the primary "go to" device at home (if the larger screen is needed and it isn't a game). With the addition of the phablet, I can't see myself ever using the iPad Air at home. Furthermore, I added the "paper" option to my various news subscriptions again; I just find the paper so much better to read. Onto eBay it goes...