for men, the mile world record has been 3:43.13 by Hicham El Guerrouj since 1999, and a little more than 1,500 athletes have broken the 4-minute barrier over 6,000 times since then. that number includes ten U.S. high school track runners and likely a few hundred U.S. collegiate athletes.
this 6,000 figure is a little bit of a low-ball though, because on the international circuit and in the Olympics, professional athletes run the 1500m instead, which is functionally equivalent to the mile but about 109 meters shorter. breaking 3:43 in the 1500m is about equivalent to breaking 4:00 in the mile, and it's safe to say many more people have done the former than the latter. nobody keeps a comprehensive list of sub-3:43 1500m runners, but about 1,000 runners have broken 3:38 (about equivalent to a 3:55 mile) per alltime-athletics.
so, is a sub-4:00 mile still the "highest" standard? it depends on how you define your terms, but i'd be inclined to say no. if you rightly assume athletes at the highest level compete for a gold medal at the Olympics (in the 1500m), being "just" a 3:59 miler won't be good enough to put you in contention. Elite milers like Asbel Kiprop can run 3:59 in the mile while sick and still finish last place in elite events like the Bowerman Mile, as he humorously pointed out on Twitter in 2017.
for women, some people consider breaking 4:30 in the mile roughly equivalent to a sub-4-minute men's time. it's a difficult mark to corroborate, in part because historically "women have had much fewer opportunities to run the Mile than men over the past 40-plus years". the women's world record mile is 4:12.56 by Svetlana Masterkova from 1996, but unlike the men's world record 1500m time, the women's 1500 record of 3:50.07 by Genzebe Dibaba is on pace for a mile time about four seconds faster than that, 4:08. given this, one might consider sub-4:25 to be a closer equivalence, but this is further complicated by the fact that Dibaba's coach Jama Aden is currently embroiled in a doping controversy calling into question the legitimacy of her world record.
to keep you humble, one thing is certain though: it takes years of dedicated training, without exception, to break 4:00 in the mile, and though some believe "any" healthy man can have a shot at the mark once in their career if he works hard enough, the most mainstream opinion is that the vast majority of men do not have the genetic talent to ever break four minutes, even with a lifetime of training. though there is less talk about sub-4:30 miles by women, i think most people would say the same of that barrier.