Is it possibe to upgrade and re-jailbreak (in order to unlock) a 3Gs running on 4.1? I have a locked 3Gs running 4.1 and it's pretty annoying not be able to install anything on it anymore (most apps nowadays require at least 4.3)

I can not unlock it officially because i bought second hand two years ago and can't reach the person i bought it from :s

So i would like to know if it will be possible to jailbreak it (to be able to unlock it) after upgrading it, or should i just leave it at 4.1 and use the basic functions ?

Modem firmware : 06.15.00

Thanks
You're a few weeks too late.

There was the Evasi0n jailbreak, which worked on iOS 6.0 - 6.1.2, but iOS 6.1.3 killed it.