Samsung Galaxy S IV codenamed 'Project J', may launch April 2013

Prominent Samsung-related blog SamMobile has the latest on Samsung Galaxy S IV rumours.
According to the blog the next generation Galaxy S device, likely to be called Samsung Galaxy S IV, is under development and is codenamed 'Project J' and may launch as early as April 2013. 

Galaxy S IV Rumoured Specs

"Samsung is having plans to announce the next Galaxy S in April.According to older rumors the Galaxy S IV would have a full HD AMOLED display, a quad-core cpu,the latest version of android, a 13 megapixel camera and the screen size would be 5.0"Our insider could not confirm the specifications at this moment! He only knows the new project name called: Project J for the next Galaxy."

Earlier rumours have indicated that the Samsung Galaxy S IV will have a 4.99-inch Super AMOLED display with 1920*1080 resolution, giving it a pixel density of 441PPI. That report is in line with other rumours which suggested that Samsung and LG are working on smartphones with full-HD display, which may be released in first-half of 2013. It would make sense for Samsung's next flagship device to be its first smartphones with full-HD display.
Other rumours had indicated the Galaxy S IV will feature a 13-megapixel camera, a significant upgrade over the Galaxy S III's 8-megapixel rear shooter. There's also buzz about the Galaxy S IV featuring a 2 GHz quad-core Exynos processor and an 8-core GPU.