I'm rather disappointed they did this on a couple of different fronts, sorry if I sound like a curmudgeon.
First, they went 19th century Brit and added the No. 2 making more confusing rounds...if they had to do this, calling it 416 Rigby Flanged would have made it self-explanatory what it is.
Second, the world doesn't need more double rifle cartridges, it needs far less of them. There is insufficient demand to overcome shortages and higher prices for components.
Third, there was a perfectly good 500/416 in existence already. Probably more 416s I've forgotten already.
Fourth, the headstamp rules. Every time you make a new cartridge, they always say how easy it is to form brass from XYZ...yet you have to get proper headstamped brass for it or its worthless. We are at present reliant on 4 businesses being afloat to ensure that double rifles can get brass: Quality Cartridge, Jamison, Bell, and Norma. (the latter making most other brands of brass private label)
And fifth, the point of the .416 is rather lost on the double rifle. The 416 shoots quite flat, allowing the use of a scoped .416 Rigby to be used at longer distances for plains game while still functioning for dangerous game. Making it a 416 double rifle neuters its long-range efficacy while providing nothing superior at close distances that what already exists with the 400H&H, the 404J, the 450NE, the 465NE etc, etc, etc.
I think Rigby is a great firm and I like Rigby calibers too, I just don't think this "innovation" helps sportsman take more game, have better access to supplies, or keeps the public safe from feeding the wrong cartridge into their rifle, it's a double-down on the problems we've got already listed above.
I don’t see it in any way as a bad thing. If a person wants to be pragmatic about it, the global hunting population could get by with maybe a half-dozen cartridges (even fewer if negating rimmed versions for singles and doubles). Part of what I love about shooting (and hunting) is the great variety. We really didn't need another .416, and yeah it is a bit handicapped in a double, but it's still a wonderful cartridge. As for ammo or brass, if in the market buy as much as you can as soon as you can as there'll be an initial run, after which the supply may very well dry up for a while. I do, however, see the new .416 Rigby No. 2 as becoming more popular than the 500/416, for reasons mentioned above. Still won't be a lot of them around, though...