FYI
The .71 update rolled out automatically on my phone either Saturday or Sunday as a Fast Track insider in the US. The phone suddenly rebooted which confirmed the update. My phone is the unlocked Lumia 950XL dual sim on AT&T network. I do not see many feature changes, but am certain there are some. Hopefully for me, a phone that starts behaving like a 4g LTE not a 2g phone with slow speed cell downloads. This would be my first issue for AT&T or/and Microsoft to fix.
As for when the update will be released, according to the post on Windows Central, Microsoft will rolling out in a country by country basis. That may explain the delay. I am not certain what country regulation that would prohibit an all at once roll out world wide.