I have a Florida Blue plan purchased through the ACA Marketplace with a subsidy. I just got a letter from BCBS yesterday that my plan is being "retired" and I will be automatically moved to a replacement plan. If I do not like the replacement plan they have chosen, I can chose another plan.
I do not know if this re-assignment of plans includes those listed through ACA, but I doubt it. My guess is that this is a way they are trying to decrease the number of ACA participants and get people into their retail products.
Their customer service is open Monday thru Friday, so I will call on Monday to find out exactly what I need to do.