It's not a redirect doing a GET, it's just a postback navigation that changes the server-side viewId while keeping the current browser page mostly intact.

I will need a test case that I can use to reproduce the issue. Exercising ace:dialog in 'showcase' (which now uses non-redirect navigation) shows me that the dialog is removed when navigating to a different demo.

I used the attached test case to reproduce the described problem. In the test the ace:dialog component is present on the second page, thus rendered after the navigation occurred. Obviously that won't make the modal popup disappear.
In conclusion this issue was a false alarm, most probably created after misinterpreting the test case behaviour.

Need button on the second page to navigate back in order to properly reproduce the issue.

To replicate the problem:

1) Navigate to the first page
2) Click the button to trigger the action which navigates (non-redirect) to page 2
3) On the second page, a popup appears. The test case may have a fileEntry component but this is not necessary to replicate the issue. You simply need a button on the popup which navigates back to page 1. The overlay provided by the modal dialog is still rendered.

The jQuery modal dialog widget append its overlay to the document's body. So the update received after navigation will remove the element that corresponds to the dialog widget but not the overlay since the renderer was never aware of it.

The fix makes use of ice.onElementRemove function to register a callback that will close the dialog widget when the corresponding element cannot be found in the page anymore.