Still in development?

Yes, the current release is compatible.

Understood. The question remains, however, whether or not W3TC will remain so. In other words, will the development continue?

Thanks in advance.

New development builds are uploaded almost nightly.

Thats great to hear there are dev versions, but where can we get them from, is it the Developer Version link under ‘other versions’ on the wordpress plugin page? 0.9.2 seems to be the latest, but I can’t find any changelist for each version.

Also, how would you go about upgrading it?

https://www.ads-software.com/extend/plugins/w3-total-cache/download/ is where the development version is obtained. To install it you have to go through the manual process of plugin installation, after uninstalling any previously installed version.