The way AS explained things when they introduced varying award pricing levels, there is still only one saver economy award bucket--W--but how that bucket is priced is determined by whether the lowest paid economy bucket is available. So if you grab the last two R fares, you should still see W availability, but it won't price out at a below-12.5k tier anymore on shorter routes. I'd assume that that link is one-way and limited to pricing, and purchasing two W fares shouldn't have any immediate effect on R availability, but I'm not comfortable instructing anyone else to make that bet.