AS of the time I am writing this post. I have a Sprint, Lumia 635, not sure of ram 512 or 1GB.
No way to tell for sure, but bottom line is it is NOT going to be upgraded as per the Upgrade Advisor in the Microsoft Store. As for me I intend to fill a formal complaint with Sprint as I think they are the one holding up this upgrade. They are also dwindling their support for any Windows phones. They don't even sell any windows phones at this time nor do they plan to do so in the foreseeable future. At least no one at Sprint is admitting that there is any things in the works about them bringing out any Windows phones.
The Microsoft website for US now shows that the 1gb is available for Sprint boost mobile and virgin. Why no att? I was going to upgrade from the 520 but definitely want to hold out for more ram.
With this update of windows 10 on Nokia 635 , is anyone going to develope a case to fit the green and orange versions which are larger than the standard black and currently not a case on the market to fit properly due to size!
On the homepage of provider KPN in the Netherlands you will also find the 1 GB version as successor of the 512 MB version:
It is tha same at Orange in Poland - it offers 635 in 1GB variant for some time now, so these devices have already hit the market.