I think it's a neat little cartridge, but will be surprised if it does not flop. Nobody, except Ralph above, seems to be comparing it to the 30-plus year old 5mm Remington. Probably don't want to put a hex on it, but the effort required to ignore the similarities seems almost comical.
The new cartridge sounds great for rifles, but the straight-walled case of the .22 Magnum Rimfire probably makes it more suitable for use in revolvers. And in revolvers, you typically have the option of switching to a .22 Long Rifle cylinder to do most of your shooting with that far cheaper round. These advantages, together with the cheaper type bullets used in loading .22 Mag. ammo mean it will be an uphill battle for the .17 Hornady.
Especially since, once you pass the price level of the .22 Mag., you could reload .22 Hornet, K-Hornet, Bee, or even beyond for the same money.