Yep, I was going to run down the list and do histories, but that prior post was long enough as it is! So I'll carry on here.
Cain and LeDuc being paired back then with other partners and both reaching the podium is of course one of the main reasons that U.S. 2011 junior pairs event is so memorable. Cain/Reagan went on to compete at senior U.S. pairs in 2012, where they placed sixth. Chris Knierim also competed in seniors that year with Poapst, doing well and placing seventh. Interestingly, Alexa Scimeca competed at 2012 senior pairs with Ivan Dimitrov. As we know, Scimeca and Knierim soon split with their respective partners and joined with each other due to Sappenfield's suggestion. A match made in heaven on and off the ice:
https://en.wikipedia.org/wiki/2012_U.S._Figure_Skating_Championships Scroll down to senior pairs
Meanwhile, Timothy LeDuc placed 11th at 2012 U.S. senior pairs with Cassie Andrews and then split, after which LeDuc paired successfully with Dee Dee Leng for a couple of seasons. Leng/LeDuc looked very promising together. However, when Marissa Castelli & Simon Shnapir (5th at 2012 seniors & later two-time U.S. champions) split after the 2014 Olympics, as we know, LeDuc tried out with Castelli who ended up choosing Mervin Tran. Leng then paired with Shnapir, and they looked good together but they both ended up retiring very soon afterward with injuries.
After Josh Reagan decided to move on, Ash Cain continued skating singles for a few years before pairing successfully with LeDuc. Reagan paired briefly with the partnerless wonder who'd reached 6th at senior Worlds with JCoughlin: Caitlin Yankowskas. But Yankowskas/ Reagan never managed to get it together competitively. Reagan eventually paired with Canada's Brittany Jones and they competed for a few years for Canada before retiring and marrying each other. Caitlin lingered around hopefully searching for another partner and eventually ended up in Great Britain with Hamish Gaman, winning the 2015 British pairs championships. Y/G eventually split, I believe due to financial and training drawbacks. Gaman had formerly been very briefly paired with Vanessa James, before she found her pairs fortunes in France.
Getting back to 2011 U.S. junior pairs, Josh Santillan skated with Olivia Oltmanns, placing 11th. They continued competing through 2012, but split afterward because Oltmanns was growing too tall for the partnership to be fruitful. Still, Oltmanns and Santillan had a lovely quality together. Of course, Santillan later found Jessica Pfund and they are still together, battling through injuries and setbacks. Santillan/Pfund have good qualities, including consistent triple salchows.
Daniel Raad who was paired at the 2011 event with Haven Denney, also competed in men's singles for a number of years. Canadian, David Leenen (paired with Morgan Sowa at that event) is Marissa Castelli's long time significant other. Kylie Duarte & Colin Grafton were a very nice looking pair coached by Sappenfield. Duarte/Grafton were 7th at 2011 junior pairs, and won bronze at 2012 junior pairs, and then disappeared. Meanwhile, A.J. Reiss who was 4th at 2011 juniors with Carman, moved on to join up briefly with Jessica Pfund, and they placed 5th together at 2012 junior pairs (I hadn't realized that). Pfund later joined with Santillan. Reiss subsequently paired with his girlfriend who came out of retirement, Erika Smith. They were speedy and very well-matched but ran into injury and training setbacks. Retiring after 2019 U.S. Nationals, Smith/Reiss are now skating for Cirque in the new production, AXEL.
Last, but not least Jessica Calalang & Zach Sidhu were 8th in junior pairs in 2011, 4th in 2012, 2nd in 2013. They then moved on to seniors where they placed as high as 5th twice. They also had some success at senior Bs along with building expectations on the GP, prior to Sidhu experiencing back problems. Of course, Calalang & Sidhu eventually split and Calalang paired with her former training partner, Brian Johnson, who'd split with Chelsea Liu (who is now training in China with Xie Zhong, as Liu Jiaxi -- Liu had competed promisingly in seniors with Ian Meyh, at 2019 U.S. nationals, before relocating).
Whew, what a musical chairs merry-go-round, that's not unsurprisingly globally encompassing.

Hopefully, the going trend is to find a good partner and stay together, like we have seen with some remarkable couples in ice dance. I wonder why there have been more long term successful partnerships in ice dance? Perhaps it's partly due to ice dance not generally exacting huge wear and tear on young bodies.