Colin
It's impossible to say as the DWP have provided no additional information beyond the announcement.
It won't be your 65th birthday it will be your State Retirement Age and it will be when you are reassessed (as we understand it) not when your award ends. So if you are flagged for reassessment after you reach SRA then your award should be revised to an On-Going award but if it is before SRA then I would expect you to be reassessed as normal but any new award should be an On-Going one.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems