I’m not sure exactly when, but it should be “soon” according to this post announcing plotly.py 5.0.0 from a few days ago.
What about Dash?
Plotly.py is always backwards-compatible with Dash , with the caveat that the version of Plotly.js being used in an app must be greater than or equal to the version of Plotly.js used in Plotly.py in order to exploit all the latest features.
Version 5.0 of Plotly.py is based on version 2.1 of Plotly.js, whereas the latest version of Dash is 1.20.0, which is based on Plotly.js 1.58.4. This means that new rendering features like the icicle charts, bar patterns and legend ranks will not be usable in Dash until the next release of Dash, or unless a 2.1 JS bundle is placed in the app’s assets directory . The next version of Dash will have Plotly.js 2.1 built-in and is expected in the coming days.