Samsung's stock just keeps rising, so the fervour associated with the new Galaxy S4 is already outstripping that of the Galaxy S2 and Galaxy S3, both of which nabbed 'phone of the year' titles in recent times.
If you needed a barometer of this, just look at how the Galaxy S3 was unveiled. Not at MWC like lots of others, but its own event, proving the Galaxy line has reached the level where it can guarantee hoards will come just for an unveiling - and come 14 March in New York, the Samsung Galaxy S4 is going to land too.
Samsung Galaxy S4 release date

The Unpacked event, which is expected to bring the announcement of the S4, has been set for March 14 2013, in New York and for 7pm EST (sadly for the UK, this means it will be midnight before you can see what's going on). And if you're in New York then, head on down to Times Square, as Samsung will be live streaming the event and will apparently have stuff to play with as well!
This means that whoever leaked the March 15 launch date wasn't too far away from the truth - but who launches a phone on a Friday? You're right. Nobody.
While we knew Samsung would eschew MWC 2013 once more for the release of its top handset, smart money tipped a May 2013 launch in keeping with last year. Samsung actually took to Twitter to discredit the rumours of a March launch earlier in the year, so there's egg on the face of whoever socially networked THAT missive..