A lot of what has been posted in the this thread about WSMs and what not... with regard to the .26 and .25 calibers was infact tried by Winchester. They were pretty hot on the idea of suping up the .25-06 even more.... however, they found that the WSM case (which is entirely new... not a necked up or down anything.... though I suspect they got the idea from Dakota, who used a .404 Jefferys case and cut it down) was most efficent in the .30 caliber. At .25, it was a barrel burner, and no doubt woefully inaccurate. Winchester, from my understanding, acctually developed the WSSM line from the desire to put a new, super hot .25 on the market... while they were at it... why not a 6mm and a .223?

With regards to calibers, as Eld put so well, just about anything to do with necking up or down exsisting calibers has been done, tried, legitimized or discarded. Any new successful round is going to have to fill a void, or else just be available enough and advertised enough to get folks to bite.

The most successful "new" cartridge that I can think of is the .17 HMR... which is just a necked down .22 mag. The rifles are cheap, the ammo is cheap... its fun to shoot, not loud, no recoil, results are explosive. You can get a heck of a fine rig for $500, and ammo is about $12/50 (price increases... used to be $9).

The hottest sellers on the market right now are varmint guns. I think that if we do see any new calibers anytime soon, it will likely be in the form of "sub-gauge" rimfires (maybe a .19 or hope of hopes a .14), which I just think are cool. No matter what though, they are either going to have to fill a gap in the market (and there aren't many of those) or be affordable enough to be justified as an extravagnacy/novelty by the average consumer.

Most innovations I think we will see in the next few years ago going to be in ammunition. New propellants, more powerful ammunition, more speed. Look at the the Leverevolution type stuff, and Remingtons "power-level" ammo. Wouldn't be suprised if we see some real advances in the ways firearms are produced too... most of it is WAY behind the times. I know someone out there is making a one piece receiver and barrel out of some super super hard/stiff metals. Supposed to be a 3.5" 20 gauge slug gun on the way too, or rumor has it.

My vote is to re-popularize the 24 and 32 gauge shotguns. Lets see a special run of Browning Citoris or BPS shotguns in either one.