2016 USA returning pool players by age by the time Olympics start:
Catchings - 37
Bird - 35.5
Taurasi - 34
Whalen - 34
Augustus - 32
Fowles - 31.5
Parker - 30
McCoughtry - 29.5
Charles - 27.5
Moore - 27
Moore has sort of been groomed to take over for Catchings on the team going forward but looking at this the obvious hole is at guard and the obvious reinforcements in the pipe line are forwards/centers - EDD, Griner, Ogwumike from the pros and maybe Stewart, Oqwumike, Thomas, and KML from college form a pretty strong pipeline when added to Charles, Moore, Parker, and McCoughtry.
There are some really good guards out there but none that have announced themselves as the next Olympians in the way that Bird and Taurasi did coming out of college nor had the immediate impacts they did as pros. It goes a little unnoticed but USA basketball has had arguably the best point guard and best combo/2 guard EVER leading the team for the past two cycles (on the team but not leading the previous cycle) and they are not likely to be replaced with equal quality. The team will need to adjust to that fact and we may see a period of less stability at guard in the coming cycles. Whalen had to wait and prove herself professionally before she got her shot at age 28 for the WC and 30 for the Olympics and that may be more typical than what we saw with Bird, Taurasi, and Cappie as well. Sims - maybe, but while she is very good will she be a better option than Vandersloot or Robinson or Wright who have a 4 year head start in the pros and overseas or Diggins who will have two years head start? The college ranks have been full of highly talented guards who have not made the national team pools let alone the actual team - partly because Bird and Taurasi blocked the way, but also because they weren't able to force themselves into the conversation with their pro careers.