Term reference on node edit to ALL vocabularies I have about ten vocabularies and my content will be tagged with mostly one term of ANY of them. 

It would be fine to let the editor choose the vocabulary on node edit form. 

Is there yet a module or patch for that situation?   It would be the core taxnonomy module, right?

A workaround would be to mount all the ten vocs into the "11th", the root one. (They have been created as mindmaps and splitted for sake of overview and because I want to use taxonomy menu and keep each one small)
The Vocabulary reference module might help you, but it doesn't even have a dev release.

A more involved solution would require adding a term reference field for each vocabulary, then placing a "controlling" list field on top of them, with an allowed value for each vocabulary. 

You could then dynamically show and hide the right term reference field using the Conditional Fields module.

The module handles required fields, so you would be sure that one term is always selected.