A letter, dated today 13 Dec 2018, from Neil Couling the Director general of Universal Credit has been posted on Rightsnet.
https://www.rightsnet.org.uk/?ACT=39...Y4p&board_id=1

This letter seems to say that Managed Migration has been put back yet again, except for a few 'pilot' cases.

In the letter Mr Couling states:

You will also be aware that the final phase of the Universal Credit Programme, after a period of piloting, is scheduled to begin in November 2020; this is the managed migration of cases which do not have a relevant change of circumstance to trigger a move onto Universal Credit.