If monometal bullets and new powders are “progress,” then short action magnums which match long action standard or magnum cartridges certainly is progress of a greater magnitude.
Maybe - due note that I don't think any of the new cartridges are *bad* - just unnecessary IMHO. When I say progress I mean the process, not necessary the direction. Trying actual new things. I don't personally see a big deal between short vs long actions. Heck the vast majority of my "short actions" are built on long actions with mag well spacers and I couldn't care less.
Also if I were in the market for a brand new rifle I'd also probably look at something popular (eg, 6.5 Creedmoor) over something similar which was already out (eg, .260 Remington), just because of simple market dynamics. I don't actively disdain a new round because its new, but that also doesn't mean that I don't think that the 6.5 Creedmoor wasn't a needless rehash of the .260 Rem concept.
Take any "new" cartridge - the brand new 7mm PRC for example which is supposed to be the new hotness. Increase the width of the base and cartridge body by another 15%. Boom - more capacity, more velocity, and more power: 7mm MegaUltraBoom(tm). Tell people that's what they need and they need to buy it. Wait a few more years, shrink it back down by 25-30% for a milder cartridge and now sell them on the idea that the 7mm Balanced(tm) is just what they need to avoid the barrel burning and heavy recoil of the 7mm MUB.
I'll give SIG some credit with the new service round in that they are trying something a little different with the bi-metal case, but honestly when it comes to just changing the shape of a brass cartridge to make it faster or slower (whichever the advertiser feels like pushing at the moment), there's nothing really new under the sun.
And a lot of buyers get bit in the process by getting rifles that are eventually associated with obsolete rounds that never take off. 6.5 Creedmoor broke through and has some staying power. Most people who bought a rifle in .30 TC aren't so lucky.
My advice is to not buy into the hype, and until proven otherwise assume that anything new will be a handloading only proposition within 10-15 years until proven otherwise. If you can live with that, then by all means try the bleeding edge stuff.