Telus always warns us "All dates are approximate and subject to change," and this is one of those times when Marshmallow upgrades are being delayed a few days. Marshmallow has been out for a few months now, and we are still waiting for many of last year's flagships to receive their upgrade. A look at the chart below shows us that several original dates are changed. The Samsung Galaxy S6 Edge Plus and Galaxy Note 5 were pushed back a few days until March 13. The big jumper here is the Galaxy S6 Edge - it moved from Marth 16 to March 30. Owners of the original Samsung Galaxy S6 can still expect their Marshmallow loving on April 13.
The Nexus 6, Nexus 6P, Nexus 5 and Nexus 5X are all due for their usual 'Security Update' on March 9, which may be the only update that stays consistent since there is no manufacturer UI skinned over top of the pure Android. The Moto X Play is getting a jump to Android 6.0.1, along with bug fixes, enhancements and a security update scheduled for March 9. Nobody likes to wait for their software upgrades and we love to blame the carrier for delays in software upgrades, but there is a long and complicated process. It could be a real disaster if an upgrade were to be rushed out and then having thousands of users calling in (if they could) with phones that no longer work. Google has even talked about taking more control over its OS in order to speed things up.
To ensure that the updates do not adversely affect the users' devices, it all starts with the "Manufacturer Testing," where device manufacturers and software manufacturers (Google in this case) perform rigorous testing of the new software. Next, there has to be "Internal Network Testing" on the carriers' end (Telus in this case) to test the stability on their networks. Then after the cellular carriers, device manufacturers and the OS provider all give their approval, it must past "Regulatory Approvals" to ensure the device meets FCC and Industry Canada regulations. Finally, it is "Pushed to [the] Customers." This process can take from four weeks to six months, especially if unexpected results occur and the process starts over. Many times in the past, a software upgrade was rolling and then abruptly stops because users reported issues and that is the last thing the carrier or the user wants to deal with.