Speculation. It's also possible that it was because of a lack of resources at Motorola. And they've just laid off a bunch more people.
in 2014, when Motorola was still owned by Google and they had done a great job getting KitKat updates out rapidly, it wasn't until May that they had an update for the 2012 Droids. That's why I think the Turbo will be lucky to get it before May 2016 - that was the best-case Motorola update performance on year-old hardware (when the Android update was released - KitKat was out on November 2013), and Motorola has done nothing to show that they are getting faster at this. (To be honest, after last year's piece of junk Lollipop 5.0 update, I think I'd want them to wait until at least after 6.0.1 or 6.0.2 was out before they even thought about upgrading anyway.)
If I were buying an Android phone right now, the only ones that I'd consider are the Nexus 5X or the Nexus 6P. I don't want Touchwiz or whatever LG puts on their phone or I'd consider one of theirs, too. It's not just Android updates - I just don't trust Motorola on keeping their phones patched for security updates anymore.
During the KitKat updates, they had these phones: first gen Moto Xs, first gen Moto Gs, and the three DROIDs + previous generation DROIDs.
During the Lollipop updates, they had first and second gen Moto Xs, first and second gen Moto Gs, DROID TURBO, first and second gen Moto Es, the previous generation DROIDs.
And Lollipop 5.0 was a disaster. Second gen Moto X Pure Edition got 5.0 and it sucked. Carrier Moto Xs got 5.0 and it sucked. Motorola got burned. I'm glad they took their time with 5.1.
Even still though, now that Nexus phones can be used on all US carriers and if updates are high on your list of features, there's no reason to buy a carrier device anymore.