As for competing in multiple olympics, it depends on the sport. Equestrian riders can complete in many Olympics as can sailors. There was a wrestler that was going for her 3rd straight Gold. The Williams sisters have competed in 4 games. These days, with the advances in training and medical care, it does seem that competitors can compete longer even in the more physically demanding sports. Gymnastics may actually be an outlier here because of how hard it is on the body.
absolutely. i think we're going to see longer and longer careers in many sports, and likely more people with multiple Olympic medals, particularly given how lucrative Olympic sports can be (Bolt, Kim Yuna, etc.)
there's only one swimmer in the top 10 of all-time medalists, Phelps. the rest are gymnastics (4 entrants), biathalon, fencing, and athletics. you get more swimmers in the top 20, but they are all Americans who make multiple appearances on relays.
it really is a mistake to look at Phelps and think that he is somehow indicative of the opportunities available to the typical Olympic swimmer. he has 28 medals, 23 of them gold. the next closest male medalist is International Supervillain Ryan Lochte who has 12. only 6 of those are gold. Phelps achieves on a level 2-3x that of the absolute best swimmers in history. we could even pretend that Phelps isn't an American, and isn't swimming on 3 medal winning relays during the Olympics, and he still has easily the most individual gold medals (and, without having to mentally and physically perform on the relays, you could argue that his individual performances would be even better as he'd have fewer overall events and more rest). on the list of individual gold medals, Phelps has the most golds (13 compared to #2 with 8) and overall medals (16 compared to #2 with 14) and he's the only swimmer in the top 10, and only 1 of 2 in the top 20 (the other being Egerszegi of Hungary).
there's a video of the Australian swim team at a press conference looking kind of shell shocked and trying to explain their lackluster performance to the media, and Mitch Larkin says something to the effect of, "i know that Michael Phelps makes it look easy, but winning one medal, let alone several medals, is really incredibly hard." and i think that's broadly true -- people who only see swimming once every four years see Phelps and think this is somehow expected or probable. it's not. it's unimaginable. not impossible, as, yes, there are multiple events in swimming and it isn't as rough on your body as running. but he's such an outlier within the sport itself.
also, i wasn't aware that there was a Gabby Douglas controversy? i guess a few people on twitter says something about her not putting her hand over her heart? these people are idiots and fools and likely Trump voters, but is this really something from which we can extrapolate "how we talk" about social issues? i'm getting tired of articles where people take a few dumb tweets as indicative of what "many people are saying" about this and that social issue. i can take (and agree with) the broader point(s), but these are awfully sweeping statements to make.