Hah, if anyone should know that this is a terrible idea, it's Conrad Black.
Not the least bit surprising that this is drawing parallels to the Black case, though. Either Cruz is dumb enough to sit around waiting for the right moment for a highly public show of renouncing his citizenship, ala Black, or he's just smart enough to realize that retaining it by bullshitting about red tape (and really, how many American conservatives are going to double check his claim?) might come in handy in the future if he gets himself into trouble.
I'm kind of hoping that it's the former. The schadenfreude from Conrad Black was just too sweet to be a one-time thing. It's probably the latter, though.