The 308 will be one of the last cartridges to go away. It's the standard NATO cartridge, as such, all military cartridges seem to maintain popularity for ever. It has gone through more testing than you can believe. For its size, it excells in power, accuracy, barrel life, throat errosion, and it feeds well. The other military cartridges such as the 223 Rem and 30-'06 Spr will stay too. Even the 99 year old 45 ACP is still one of the most popular military based pistol rounds.