This is depressing. Trello is a beloved software for a lot of people. It's sad that Trello decided to sell off to Atlassian. I can't believe the same company that makes Jira is going to run Trello. SourceTree is the only software that they make that doesn't suck.
For sure they won't change Trello to become like JIRA, and there is a little hope the JIRA UI will become more like Trello. So IMHO nothing to worry about.
I like Jira but I understand why others aren't fond of it. I'd argue it completely depends on how you configure/use Jira. Administering it is annoying regardless though.