iPhone 3GS 3.1

[metfuel]

I have a 3GS that I got a couple of months ago after my 3G took a crap (I have gone through jailbreaking before so I know what I am doing, mostly).

When I got the 3Gs I wasn't too comfortable when I found out that pwnage tool was not available for the 3Gs and did not want to try purple rain or redsnow. I upgraded to 3.1 when the update came out through iTunes, and zoom ahead to now when pwnage is finally available for the 3Gs. From every discussion I have seen it seems that mostly people are talking about jailbreaking their phones and unlocking them to use on other networks. I understand that if you upgrading your phone the normal way through iTunes to 3.1 will kill your chances of unlocking it for other networks, but since unlocking is the only issue I have seen I am going to pose my question.
Does the upgrading to 3.1 on a virgin iphone 3Gs through iTunes also kill the opportunity to jailbreak only (not unlock) the phone. Or can I still jailbreak my phone using pwnage and a custom 3.1 firmware?

[nickswagger]

As of now, I believe so. But I hope there's a fix around the corner