'So are you assuming that because BREXIT was a vote against the establishment, then any future elections - parliamentary, council etc - will also be 'against the establishment', irrespective of the specific issues at stake?'
No, because the Establishment is not always wrong and is not always out of touch with the majority. They get some things right.
'How long do you think that 'the majority of the people' will continue to vote anti-establishment? '
For as long as the Establishment and metropolitan elite remain out of touch with the people (the majority).
'Is that why Teresa May has chosen not to call an early GE?'
I don't know, but she has an important job to do, to deliver the will of the people over Brexit and possibly thinks she is the best person to deliver that and that the "magic circle" may not show the same willingness to deliver the will of the people.
'What about next years council elections and the upcoming mayoral elections? Will 'anti establishment' candidates be running in order to give 'the majority of the people' the opportunity to vote for them?'
I think so. My guess is that UKIP will still do well as lots of people still think that the Establishment candidates are not listening to the people.