I interpreted the press release to indicate that WiFi HaLow will be 900 MHz only, but can coexist with traditional WiFi implementations on 2.4 GHz and 5 GHz. (The Wikipedia page seems to confirm this: https://en.wikipedia.org/wiki/IEEE_802.11ah) Just like when 5 GHz was added, this means getting a new WiFi card -- but that card could support all three bands at the same time.
So this would mean while you're near an AP you'll be on "classic" 2.4/5 GHz, but when you roam further away it would switch to 900 MHz "HaLow" for longer range.
So this would mean while you're near an AP you'll be on "classic" 2.4/5 GHz, but when you roam further away it would switch to 900 MHz "HaLow" for longer range.