I can't answer all of the historical questions, but here's what I do know. The first zoo to house Komodo dragons was the Bronx Zoo, starting in the 1920's. That being said, Bronx Zoo hadn't consistently held dragons for that entire time, National Zoo likely has the longest continuous duration housing the species out of any zoo. There have been a number of new holders in recent years. While I don't know who is the exact "most recent" holder, some recent ones include Roger Williams Park Zoo (2017), Buffalo Zoo (2018), and Rosamond Gifford Zoo (2019). They've even made it outside the AZA in recent years, with Montgomery Zoo starting to house the species in 2020.
As for further expansion of holders, it's possible. After breeding started in the 1990s, there was a big rise in the population from around 2010-2014, explaining the rise in holders that ensued after that. Since 2014, however, the population has stayed relatively stable. Komodo dragons do face some common challenges that likely make it a difficult population to manage, specifically variable litter/clutch sizes and unpredictable breeding.
Typically, populations with highly variable litter/clutch sizes can be a challenge to manage, causing "boom and bust cycles" with rises and falls. This challenge has caused problems to the African wild dog and warthog populations, and given Komodo dragons have a very variable litter side, it's possible going forward this could cause a big issue for the Komodo population too. Of course, the fact Komodo dragons have a history of parthenogenesis complicates matters too- as this can mean females who aren't "supposed to" breed genetically end up producing offspring, and given the unpredictability of this and that there are genetic and sex-ratio implications to this, I'd imagine the population has additional, unique challenges to manage too.
