A fifth candidate release ("RC5") of WSJT-X 2.0 has been Available for download and use by beta testers since 26 November. The "Quick-Start Guide to WSJT-X 2.0" has been updated, and must be read thoroughly before using RC5:
http://physics.princeton.edu/pulsar/k1jt/Quick_Start_WSJT-X_2.0.pdf "RC5 is stable, works well, and fixes the known problems in RC4. It is likely that the General Availability (GA) release of WSJT-X 2.0, scheduled for 10 December, will be nearly identical to RC5.
We recommend using RC5 (and therefore the v2.0 FT8 protocol) in the conventional FT8 sub-bands at audio TX frequencies 2000 Hz and higher.
Inevitably the necessary transition from v1.x to v2.0 protocols for FT8 and MSK144 will cause some confusion and cross-protocol interference. Users of v1.9.1 and earlier are unable to decode transmissions from users of RC4 and later, and vice-versa.
As more users upgrade their software to WSJT-X 2.0 - and particularly after the General Availability (GA) release on 10 December - the new protocol should start to dominate the conventional FT8 sub-bands. As soon as possible after 10 December, and certainly by 1 January 2019, everyone should be using WSJT-X 2.0 or a compatible v2.0 version of derivative programs such as JTDX or MSHV".
Download links for RC5 on Windows, Linux, and macOS can be found on the WSJT-X web page:
http://physics.princeton.edu/pulsar/k1jt/wsjtx.html.