“To come here and win the omnium is massive for me”
Kenny, 24, earlier needed only two heats of a best-of-three men's sprint semi-final to beat 36-year-old Hoy.
France's Gregory Bauge then beat Kenny to gold in the final, with Hoy taking bronze over Australian Shane Perkins.
However, with only one place available to GB in the Olympic individual sprint, Kenny's semi-final victory might have preserved his London hopes after Hoy outperformed him at February's World Cup.
Trott is assured of an Olympic place after picking up her second world title of the week, alongside the women's team pursuit title she helped to win on Thursday.
The 19-year-old has yet to stand anywhere on the podium except at the top: all six medals she has now won at senior European and world level since emerging in 2010 have been gold, and she has turned the omnium's elimination race into her own entertaining signature event.
Leading overnight following Friday's first three events, Trott placed third in the individual pursuit, 13th in the scratch race and first in the time trial to secure the overall world champion's rainbow jersey.
Kenny beats Hoy in sprint semi
"I think I'm setting myself up well for London," Trott told BBC Sport's Jill Douglas. "To come here and win the omnium is massive for me.
"I've never been in that position [of going] into the last event winning. It was really hard on my head but I got myself fired up for it.
"Me and my coach have been doing a lot of work, watching back the races that I haven't done so well in, and it's paid off. I improved on the points race, which was that extra margin I needed from the London World Cup."
Kenny lost his own rainbow jersey to Bauge in an intriguing sprint final inside Melbourne's Hisense Arena, with the formidable Frenchman powering through the first heat before Kenny looked to have caught him cold with an early dash for the line in the second.
The Englishman did not get the chance to test the now tired-looking Bauge in a decisive third heat, though, as he was judged to have gone off the sprinting line, handing his opponent a 2-0 win.
Bauge won the event last year but was later stripped of the title as a result of a 12-month retrospective ban, imposed by his own national federation, for offences related to dope tests.
Kenny, beaten by Bauge in the 2011 world final, was racing as the defending world champion having been elevated from silver-medal position, but Hoy is the Olympic champion - he beat Kenny in Beijing four years ago.
Since that battle of the Brits, world governing body the UCI has altered the Olympic cycling rules: nations now have only one entry per event instead of two, hence Hoy and Kenny must scrap it out for the one place available to Britain at London 2012.
The British Cycling team for the London Olympics is expected to be announced in June.
who won a gripping women's sprint contest despite a collision with arch-rival Anna Meares of Australia on Friday, ran out of steam in her keirin second-round race and failed to join Meares in the final, which the Australian won.
won his second medal of a highly impressive week, following up Wednesday's scratch race victory with silver in the points race behind Australian Cameron Meyer. Neither event is in the Olympic programme.
finished fifth in the men's individual pursuit, which was also dropped from the Olympic schedule following Beijing 2008.
BBC coverage (times BST):
Medal sessions live on BBC Sport website and Red Button from 1000 each day. Highlights on BBC Two 1430-1700 Sun 8 April. Commentary and updates on 5 live and 5 live sports extra 0500-1400 daily.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.