They would make extra money in expansions for it would be accumulated DLC with probably major content changes.
Yep, either some people will end up paying for the civs they already bought through DLC again so they can get the content changes from the xpacs, or the content changes will be sold without new civs from now on (at the same price of course), or maybe they're switching from xpacs to pure DLC so they can exploit us for more money while ultimately providing less.