According to a tip sent, Samsung 4K AMOLED screen is 6" in diagonal and packs a pixel density of 743ppi.
Take this information with a pinch of salt, of course, but it's very likely for Samsung to be considering this. The Galaxy Note family of smartphones grow ever so larger in terms of display, so a 6" would be a logical evolutionary step for the Galaxy Note 5.
Moreover, a recent set of rumors suggest the Galaxy S6 will be powered by an Exynos 7420 chipset, which would have four Cortex-A57 cores and four Cortex-A53. We wouldn't be surprised to see this configuration in the Galaxy Note 5 as well.
Traditionally, Samsung launches a new Galaxy Note smartphone in the fall at IFA consumer show in Berlin, Germany. There's a lot of time until September 2015 and the Galaxy S6 is the first of Samsung's flagships to be anticipated.
