Originally expected to be unveiled at MWC as the last few Galaxy S models were, Samsung announced at MWC through a video that the unveiling would take place on March 29th this year. The April 21st launch date has been rumored for some time.
So what caused the delay? There are a couple of theories. One is that Samsung had to match production of the phones with Qualcomm's shipping dates for the Snapdragon 835 chipset. The other theory is that Samsung wants to double and triple check everything to make sure that there is not a repeat of the Samsung Galaxy Note 7 fiasco. Back in January, Samsung announced a new 8-step battery test to make sure that the juicers used on the new models are safe.
UPDATE: According to a subsequent tweet from Blass, the reason for the delay could be due to both Qualcomm and Samsung achieving low yields with the production of the 10nm Snapdragon 835 and Samsung Exynos 8895 chipsets.
If you've already circled your calendar or have set a reminder on your current handset, you might want to make the change now. The rumor calls for just seven additional days of waiting, which you should be able to handle.