do you think 600 expansion will be as widespread as T-Mobile makes it sound like? I know they got nationwide licences so hopefully it won't be a sporadic build here and there.
The biggest gating factor is not under T-Mobile's control. In order to deploy anything on 600MHz, they have to first migrate any remaining UHF TV stations off those bands. And I believe there are quite a few stations still operating in there. The FCC establishes exclusion zones within... I think its like 100 or so miles of a TV station operating in that band.
Now, as part of the transition agreements, those stations are supposed to move off. But these things can take time. I think T-Mobile might be assisting a bunch of them to be honest.
Remember that T-Mobile won the 700Mhz spectrum in 2007... and it took a good, what, 6 or 7 years to start rolling that out? It was a more crowded space, granted, but it's still not easy.
That being said, the Note 8 will not nor ever will support 600MHz. But there's an extremely good chance that anyone picking up a Note 8 will have moved on to their next phone by the time they get 600 in their area. If you ARE one of the ones that will see it soon, and you need it (which is a small number by the way), yeah... don't get a Note 8 and wait for a 600 supported phone.