The Galaxy S4, aka GT-I9500 or Altius, has been developed under the name Project J and could be announced in March. Well Project J now consists of a total of three devices, based on information about upcoming accessories via SamMobile. See also: Samsung Galaxy S4 release date, specs and rumours.
Samsung's Project J mini, codenamed Serrano, hints towards a smaller smartphone which would be the Galaxy S4 mini. This isn't exactly an outragious claim since Samsung has launched the Galaxy S3 mini to sit alongside the full size Galaxy S3.
SamMobile says the Galaxy S4 mini uses almost the same accessories as the Galaxy S4 but won't feature wireless charging. It is likely to be a cheaper and lower spec version of Samsung's new flagship smartphone.
The third device is called Project J Active, codenamed Fortius, and hasn't been full decided upon. It will come with accessories including an arm band, bike mount and pounch suggesting it could be a smart watch. Samsung might call it the Galaxy Watch but alternatively it could be a smartphone similar to the Galaxy Xcover 2.
See also: Apple testing smart watch designs.
It has been suggested that Samsung will announce the handset outside of MWC (Mobile World Congress) on possibly 15 or 22 March. It will then be released and go on sale some time early in April.