The Canadian carrier Rogers has just started seeding the Samsung Galaxy S4 Android 4.4 update today. Subscribers should be prompted to update over-the-air, the update is about 150MB in size, so keep your Wi-Fi close and your charger closer.
Also, Rogers confirmed that KitKat is heading to the HTC Desire 601 (late March), Samsung Galaxy Note 3 (late March), and Sony Xperia Z1 (coming soon).