I do think that a revolver probably is outside of most D&D games, the pistol/musket as written in the playtest I have no problem with. As I can only 'judge' what is in the playtest and not some future product that might or might not transfer to the end product of this playtest, I think reffering to unknowns and judging something (the gunslinger class) based on assumptions, is a bit like jumping the gun ;-)
May I direct you to Ed Greenwood's Golarion web fiction on Paizo's webpage:
http://paizo.com/store/byCompany/p/paizoPublishingLLC/pathfinder/tales/serial
Unfortunately, Alkenstar is in Golarion.
Fortunately, to date at least, per the Campaign Setting, the influence of firearms has been minimal as magic is more effective. Players, on the other hand, often choose not to conform to campaign setting canon & frameworks. So when a PC wants to try out their shiny new gunslinger, you can say they can't find any ammo, but there are countless posters on this site alone that will tell your player that you're being a crappy GM for limiting the player's "fun".
Frankly, Greenwood's Alkenstar web fiction is as jarring to the setting as the (thankfully) aborted/redacted artwork of pith-helmet & cartridge-firing rifle-weilding explorers that debuted early in the setting's history. It DOESN'T FIT.
There are plenty of things that are cool. Not all of them belong in a single campaign setting. Some people like guns in the frpgs. I get it. But I think advanced firearms & a gunslinger class take it too far, and since I'm not a fan of the retcon, I'd prefer not to throw open this particular Pandora's Box in Golarion. The fact that it was cracked open at all was quite enough for my tastes. YMMV.