I'm a big fan of Trello but I dread using Atlassian products. I do not have a good feeling about this. Hopefully Atlassian can learn from what makes Trello so wonderful instead of JIRA-ifying it into oblivion.
Funny how much opinions can differ. I've used them both professionally and I think Trello scales poorly above 5-10 people while Jira is the least-worst option for running a project at any team size.
If you have more than 5-10 people using each of your task boards, the problems may be more than any productivity tools can really fix.