The Galaxy S4, when it launches later this year, will sport a 4.99in screen with a Full HD 1920 x 1080 resolution, according to Anandtech. The Samsung roadmap shows a planned launch of a FHD display in Q1 of 2013. See Samsung Galaxy S4 and Note 3 could have flexible displays.
The photo shows the screen as a follow-up to the 5.55in found on the Galaxy Note 2 and 4.8in of the Galaxy S3. If Samsung's Q1 smartphone is the Galaxy S4 then it will have a screen with a pixel density of 440ppi.
This would make sense seeing as a number of smartphones announced at CES this year featured 5in Full HD screens including the Sony Xperia Z, Huawei Ascend D2 and ZTE Grand S. It would mean keeping up with the Jones' at least.
Something which could make the Galaxy S4 stand out from the crowd is the possibility of a curved section to the display, rather than a fully flexible device like the Youm shown off at CES. Anandtech looked at some concept Samsung devices which had either a curved side or bottom.
When a flip cover is in the closed position, the curved part of the screen remains exposed for notifications and other information such as the time. The small curved section can be lit up on its own rather than the entire display thanks to AMOLED technology.
It's also highly likely that the Galaxy S4 will be powered by Samsung's recently announced Exynos 5 Octa 8-core processor.
It seems doubtful that Samsung will announce the Galaxy S4 at this year's MWC since it decided to hold its own event afterward for the Galaxy S3 launch. Therefore, March would seem a suitable month for the Galaxy S4 to make its debut.