Have a hard time believing anything from sammobile these days, have got so much wrong in the last few years i.e. GS 4 was supposed to have a metal chassis, LCD screen, GS 3 was suppose to have a ceramic back etc.............
Besides, it is not exactly hard to guess what it will be like going by the note I/GS 2 and note II/GS 3

I am just expecting the usual spec bump:
- slightly higher clocked CPU
- same camera as the GS 4
- 3GB RAM
- 16GB/32GB storage options with SD slot
- 1920x1080 SAMOLED screen (maybe a bit higher res.)
- Spen
- same design, materials, build etc.
etc.
Still don't see how they are going to increase the screen size to 5.9" without making this one huge phone, note II bezel is already stupidly thin, more or less the same as the GS 4 except for the side bezels and even then there is barely much difference, only way they could pull it of is literally to have edge to edge and lose the Samsung logo on the front, which most definitely won't be happening!
But then if they manage to pull it of, they run the risk of the phone being very fragile (assuming they use the same screen/panel as the GS 4) as the GS 4 screen already seems weaker than other phones screens.
There is just no way they can add 0.4" to the screen and keep the same measurements of the note II, going to be
at least a 2-3mm increase in width and height (those two dimensions matter most from my experience, especially the width for when it comes to one handed use)
Is 4GB RAM really necessary? 1GB let alone 2 tends to suffice. Unless the next version of android requires some serious computing power 4GB ram just seems like boasting rights.
Just a typical android spec bump really, keep bumping the specs for no real reason other than for purely marketing and also because they will need to make sure it is very good as HTC are getting into the phablet market now. Anything above 1GB isn't
necessary (especially with light skins that are well optimised), however, 2-3GB is a nice
luxury imo, more stuff stays in the RAM, so means everything should start back up literally
instantly and nothing will reload etc.
EDIT:
In fact, you can probably expect the dimensions to be more or less the same as the galaxy mega 5.8" (although it has a smaller battery than the note II [2600 mAh ])
GM 5.8"
162.6 x 82.4 x 9 mm
GN II
151.1 x 80.5 x 9.4 mm