Disclaimer: I'm a member of wxWidgets dev team, however I'd still like to reply to this to give some facts which hopefully don't suffer from any bias.
- wxWidgets is still being actively developed, the development simply happens almost exclusively in 2.9 branch and not 2.8. You can look at the activity timeline to get some metrics. The last release was indeed in July and the hoped for autumnal release couldn't be done soon enough so it will now be done in January but this is hardly the end of the world.
- If there is a single platform where wxWidgets should be used instead of Qt, it's OS X. wxOSX is far from perfect, and I'm well placed to know of its problems, but it still provides a much more native user experience than Qt there.