It's good to think about possible attacks so we can look out for them.
Privacy is a multi-faceted idea. I don't think CoinJoin or JoinMarket entirely solve the problem. A single CoinJoin does nothing to help with time-based or amount-based privacy invading, because the deals happen apparently instantly, and if you send in an amount of bitcoin you'll get back out that amount minus fees.
Yes. Nevertheless, I really think that JoinMarket could be "the" CoinJoin solution that actually takes off - due to the inherent profit incentives. This would make it at least one important tool for privacy.