But you must also note that the 10mm has been around since the early 80's and Sig finally decided NOW to go for it. Hmmm.
Well, but the market for the 10mm has hardly been static since 1983. Hugely popular early, then bankruptcy for Dornaus & Dixon, then revived in 1987 by Colt's Delta Elite, then peaking with its adoption by the FBI, then seemingly "dead" after the arrival of the .40S&W.
And you know the rest, ... thru most of the '90s the 10mm became a "dead" - or at least a dormant and watered-down cartridge - until Glock introduced the G29/G30 compacts, S&W brought back its 4" 610 wheelie, and in the early 2000s Texas Ammo Company became the first so-called "boutique" (i.e., family-owned) ammo-maker to start marketing full-throttle 10mm ammo, using XTPs and some of the then-newer bullets (Gold Dots). I still recall reading the write-up on TAC's line of full-spec 10mm ammo in one of the gun rags. TAC preceded DT, BB, etc., by at least 2 or 3 years. And somewhere in there Tanfoglio's 10mm Witnesses arrived (like 'me or hate 'em).
And today, aside from Sig's 4 10mm models, we have the new 10mm long-slide Glock .40 on the way. The Turkish Sars K2 is shown as a 10mm model, although EAA doesn't yet import it; supposedly GrandPower is developing a 10mm model; and depending on how you read the tea leaves in the most recent (Jan.2015) announcement by Vltor's CEO on the "improved" Bren Ten project, they still intend to produce the "Legacy" model, possibly to be seen in 2016.
Not to mention Federal, hardly a boutique ammo company, which gave us the first downloaded 10mm load for the FBI's use in 1989, came out last year with a new (and mostly) full-spec 180gn trophy-bonded load. In fact, more ammo companies are making more varieties of 10mm ammo - up and down the huge energy curve - than at any time since Norma first introduced this cartridge.
So, when you take the long view on the history of the 10mm AUTO, I'd say its resurgence is continuing, maybe even at a significantly increased pace. My advice would be to stay optimistic. My sense of it (and I go back to the late '80s w/ this cartridge) is that the 10mm's popularity among American handgun buyers generally is growing - even among those for whom the 10mm isn't their initial or preferred round of choice. Shooters seem to want
at least one 10mm pistol in their collection. And personal subjectivity aside, there must be a market-based reason that the gun and ammo companies are detecting in what is unquestionably a "niche" cartridge.
Besides, who knows what R&D into other makes of 10mm pistols by other gun makers the new Sigs and the new G40 will spur? - those who've discontinued previous models, perhaps, or those who may have one in development "on the backburner," now to be moved to the front?
A "10mm" 97B from CZ?
Who knows?