Any DLC that would likely be profitable is going to be made.
Zulu, Portugal, and Sumeria are probably the most likely to be next. After that we might see Poland and Brazil. Canada is a possibility too, although I hope they don't package it with Australia if they do that. I'd consider buying Canada, but not if I have to get Australia to get it. I do expect one or two "left field" DLCs eventually though, so that could be one of them.
Zulu, Portugal, and Sumeria are probably the most likely to be next. After that we might see Poland and Brazil. Canada is a possibility too, although I hope they don't package it with Australia if they do that. I'd consider buying Canada, but not if I have to get Australia to get it. I do expect one or two "left field" DLCs eventually though, so that could be one of them.