Best place to keep an eye for updates is over here Software updates It lets you know what devices are in what stages of update, if updating at all! It's not 100% since sometimes more is communicated for some devices than others, but it will house all the publicly available info!
Hi.. I looked on that page and there is no listing for the V20. The V10 is listed but not the V20. As you may know, there is a security issue fixed in the July Android update to Nougat. Is that being pushed by T-Mobile to the V20?
https://blog.exodusintel.com/2017/07/26/broadpwn/ has details on the vulnerability.