The Samsung Galaxy S6 will have a 5.5 inch display or higher, probably.
The French site nowhereelse.fr based on an accesory particulary a case (picture above) for the upcoming Samsung Galaxy 6 is suggesting the smartphone might come with a 5.5 inch display., based on the following dimensions:
Galaxy S6: 143.52 m.m high, 70.70 m.m wide (72.94 m.m with the buttons) to a thickness of 7.19 m.m
Galaxy S5: 142 m.m high, 72.5 m.m wide and 8.1 m.m thick.
We drew the Galaxy S6 diensiond on a paper and if you do the same you can see the diagonal gave us more than 6 inches, so we don`t know how Samsung is going to shrink all to get a suggested 5.5 inch or less.
The Samsung Galaxy S6 might be coming with:
A Super AMOLED Display at least 5.5 inch with a resolution of 2560 x 1440.
A Exynos 7420 Octa Core processor 64 bits.
3GB of RAM.
20 Mpxls rear camera capable of capturing video in 4K.
A 5 Mpxls front camera.
Finger print ID sensor.
Heart sensor sensor.
Full metal case covered wih a later of glass.
At MWC 2015 2-5 March 2015, Samsung will bring the final product up.