While it seems to be the aim to merge the entire former OS flight operation into VO, indeed the AOC seems to be an issue. Neither AOC nor OM-A at VO cover long range or augmented crew operations at the moment; I do assume that this will be amended until the amalgamation is set in force. Currently, 1st of July is eyed as first possible date; no further information on this has leaked until now.
Whether the OS AOC will be kept alive for brand name reasons, I do not know either - if I may speculate, I will look at Swiss who apparently has allowed some small US charter corporation to use the old Swissair brand in order not to forfeit it (see
Swissair hebt wieder ab - News Wirtschaft: Unternehmen - tagesanzeiger.ch - in German only unfortunately) and assume that OS might consider the same strategy.
We shall see what happens - interesting times indeed...