With the implementation of the merit system, I don't think holders of several accounts would be encouraged to maintain their alternative accounts especially if their posts aren't recognized or merited
But it can be lead to exchanging of merit if a person have multiple accounts even his post is not recognized by others he can used his alt account to give merit.
There are certain campaigns now that require a significant amount of merit scores.
Yes, Manager Yahoo62278 already included merit for choosing participants in his campaign handled.
It would be hard for them to handle accounts and apply to campaigns especially when the requirements are not met accordingly. Maybe due to this, they would rather just focus on one account to assure profit.
I think we can not assure that they only focus in one account but the important is the merit system helps to lessen the spammers and make all the member will be more responsible in every single post they made.