We plan to release 3.0.1 on June 15 (this year, before the jokes start coming in). There have already been a lot of changes since 3.0.0, with many important bug fixes in all three main ports, including tons of corrections to everything bitmap/alpha-related in wxMSW by Artur Wieczorek who managed to eradicate swathes of long-standing bugs, so we'd like to make these improvements available as soon as possible. However we'd also like to ensure that we haven't broken anything since 3.0.0. And while we are relatively confident that the ABI hasn't changed, the behaviour of the code is another matter and some new bug(s) could have been introduced in almost half a thousand commits since 3.0.0.
Which is why it would be really great if as many people as possible could test the 3.0 branch sources before 3.0.1 is done, in two weeks time. Regressions are usually found quite quickly after each release, which is great, but it would be even better if we could find at least some of them before releasing it. So if you are using 3.0.0, please grab the latest 3.0 branch sources using either Subversion (https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH) or Git and let us know if you see any new problems.
Thanks in advance!