This reminds me of the exchange between Tom and B'elanna right after their wedding. It went something like:
TOM: So, B'Elanna Paris... Has a nice ring to it.
B'ELANNA: Actually, I kind of like the sound of Tom Torres.
TOM: You're joking.
B'ELANNA: Why not? It is the 24th century, you know.
So it seems couples are still having debates about this hundreds of years from now.
To the poster who said that the U.S. is the only Western country where women taking their husbands' names is still common, it still happens often here in Canada too. Personally, I think it's an archaic custom, but as I'm unlikely to ever get married, it's one I won't have to deal with anyway.
As for the original topic... eh, I don't see Seven changing her name if she marries Chakotay. And who knows what is typically done in Chakotay's tribe? I think they'd both just keep their names (or designations) as they are.