Samsung sent out invitations to their 2nd 2015 - "Galaxy Unpacked Event" that will take place in August 13. Samsung will probably unveil the Galaxy Note 5. Here's the event invitation:
As you can see, Samsung is clearly hinting at a curved design - and this invitation is very similar to the Galaxy S6 event invitation sent out in early 2015. We wouldn't be very surprised to see a curved variant of the Note 5 - after all the Note 4 had its own single-side curved variant (the Galaxy Note Edge) and the GS6 Edge is very successful - beyond Samsung's own expectations.
Following this success, maybe Samsung will finally ditch glass-based OLEDs altogether and release only one Note 5 model - one with a curved flexible OLED display? Samsung is also developing foldable OLEDs, and at one point the company aimed to bring these to the market in 2015, but it seems a bit too early for that and foldable phones that turn into tablets will probably only arrive in 2016. Anyway we'll know for sure in two weeks.