Just had an interesting phone call with T-Mobile today.
I've been bouncing emails and playing phone tag for awhile now and got pushed up the escalation ladder (I believe I got to the top of the ladder with the presidents office). What I found out was that it was a mutual agreement with T-Mobile and Nokia to not push out the "Black" firmware due "critical" bugs in the firmware with the Lumia 810. They wouldn't go into specifics, but suffice to say, they said they were "severe bugs" that justified not pushing it out.
Now, as for what about getting "Cyan" and WP 8.1... With all my wrangling, open ended questions, talking around the topic, I could only get "We still support the 810". No poking, prodding, or anything, could I get past the standard corporate answer, and that if they get any updates from Microsoft/Nokia that pass QC they will pass them along to the end users. (Man my social engineering skills are slipping).
One thing in all my digging, is that everyone I had conversations with, praised the 810 as being their personal favorite phone (only if they actually used the 810, I did have to deal with some that hadn't, so they had no clue), and they too were upset as to it's current status of EOL. Most of them mentioned the 925, the 521, and the HTC 8X (and a couple model numbers that I haven't heard of, ANYWHERE), but they personally said they preferred the 810 over all of the Windows Phones that T-Mobile offers/offered. Those that had that opinion, said in a round and about way, that they are still fighting for the 810 internally in T-Mobile.
So again... any more updates (Cyan/WP8.1) for our beloved 810's? Sadly, I don't know.