AT&T Unlimited LTE Hotspot $20 without AT&T phones

So what happens when they decide to raise the price in a year or two or less? Those that sign up for the 2 year plan might actually get the better deal in the long run if they do increase or just eliminate it all together.
The secrecy of this device and plan has me wondering. Is it just to fill a niche market that wants cheap mobile internet service without revealing it to the masses? Is it just a trial run? The availability of the Mobley is almost non-existent now.