Actually topbonus is owned by EY (70%) and AB (30%).
I think, the next 2-3 months there will be no problem with existing bookings.
If there are problems with existing award bookings on AB metal, where AB is not the marketing carrier (not 745-tickets), the passenger will be rebooked or refunded.
I'm afraid, there will be problems with existing topbonus awards bookings (745-tickets) after the 2-3 months periods. There is a high risk, that the passenger has to rebook on his own costs. Especially on airlines, which don't belong to EY. The risk of total loss with tickets on EY metal is maybe a bit lower, but still significant.