I somewhat doubt that Operamail accounts are the lifeline of Fastmail - if they are then the company is in serious trouble!
There's currently some half a dozen of us bemoaning the loss of the Operamail address here on the forum and of that number at least half have decided to move on to pastures new.
If those committed to saving Operamail numbered even in the low few hundreds that might perhaps indicate a glimmer of interest in the future of the address and raise the hope that some form of determined collective action could win the day. But I can't see the critical mass required being reached in a month of Sundays - I hope you prove me wrong.