They did raise or remove the limit I believe, though long lines, particularly minified files, do still pose a problem and force me to kill Atom.

Edit: Confirmed that the 2mb limit was removed. While viewable and editable, depending on the operation you attempt you may see issues.

I tried copy/pasting the contents of a 3mb json file several times and eventually it caused exceptions to be thrown (but no crash). Same test worked in Sublime Text, albeit with freezing. They do still have some work to do on the edge cases but it's been nice to see progress.