It is currently hoped that the next Beta Test release of Poweramp v3 will be ready sometime in April 2018. For the latest update posted by Max the developer, please see http://forum.powerampapp.com/topic/10136-poweramp-v3-project-update-please-read-first-post-for-latest-info-before-commenting/?page=77#comment-46297
As you are probably aware, the Poweramp developer, Max, has been working hard on an updated material design user interface for Poweramp v3, which required a full ground-up rebuild of the code so has taken over a year to develop. Note: this update will be included within the original purchase of v2, there will be no extra licence charge for existing users.
It's not quite ready to be released for open testing yet, and it's very hard to predict the exact development time. Requests for ETAs are pointless, and will not make it happen any quicker! Max has all the custom components ready (buttons, new Album Art effect, lists, grids, now bottom navigation, etc., with everything animated) but during assembling - partly due to his attention to the fine details - it is taking a bit more time than anticipated to ensure it works properly across the diverse Android ecosystem. He doesn't want to just release it as is, with jerky animation and some non consistent behaviors on some devices.
Slide-in side menus (drawers) have been dropped completely. All user interface and navigation is now gesture and button driven, and the primary supplied skin will be white. However when using visualizations a black background will be used as they cannot be rendered on white. A black themed skin will also be provided.
Third-party skins will need to be redesigned for v3, and Max will be releasing the documentation for that closer to the main app release. The final release will include fixes for all supported hi-res audio devices and more (mostly Chinese) brands. There won't be any other major changes to the existing alpha-test audio engine or effects.
The next beta release will basically be close to the intended v3 release, so effectively feature complete, and the official release will hopefully follow shortly. There won't be a lengthy delay like there was between alpha and beta. Also, Poweramp v3 will be Android 5.0+ (Lollipop+) only, although the old PA v2 version will get a few bug fixes and will remain available for users of Android 2.3 - 4.4.
Max has said he will become more active here on the forums once the beta-test is released to catch feedback.
Once the official v3 release is complete, Max will turn his attentions to building new features for 'v4', which will include:
Audio effect plugin framework, with sample projects.
More configuration options for existing Poweramp DSPs (e.g. parametric equalizer interface and selectable 5-8-10-16-24-32 EQ bands).
DLNA/Chromecast output (if Google will stop changing the Chromecast APIs all the time!).
A tablet-specific user interface (there is no specific tablet layout included with v3).
For previous progress reports, see http://forum.powerampapp.com/index.php?/topic/10136-Poweramp-v3-project-update/&page=8#comment-40253 and http://forum.powerampapp.com/index.php?/topic/10136-poweramp-v3-project-update/&page=11#comment-40719.