Yes, it will almost certainly have 4.0.2 on it now, so you would have to wait for a JB on 4.1 to be released, which could be any time from weeks to months...
it's a gamble but worth it I think. 4.1 OS is not far away maybe during next weeks events who knows. but it will be out soon. once it's out new jb will be out soon since the Dev-team has found two other exploits. they are just waiting for Apple to release a real firmware upgrade. I say order your I4 wost case I promise it won't be long before you can jailbreak.
Almost guaranteed not to have 4.0.1. They have a hard enough time keeping them in stock. 4.0.2 has been out long enough. If you have a 3GS already that's jailbroken, then wait. If you don't have any iPhone, then a non-jailbroken iPhone is still better than no iPhone at all.