I can i still upgrade my iphone even if its jailbroken?

I want to jailbreak my phone but i'm afriad if i jailbreak my phone i can't upgrade to the iphone 4s

Yes you can. If your older Iphone is Jailbroken, all you have to do is restore the Iphone to it's Factory (Default) settings directly from ITunes. The instructions should be in the instruction manual.

Yes you can but once your ready to upgrade! Restore it back to original settings by connecting to iTunes & clicking the restore button! It will erase all your jb data! Don't take it to your carrier jb. I have my 4s jb, but once they announce d new iPhone on Wednesday. I'm going to restore it & sell it & get d new 1. If it has all d features rumored. As in 4g & bigger screen! So you might wanna wait to upgrade. The rumor is announcement wednesday & release on the 21st! & they've been right about announcement, so it's probable. Choose wisely!