The HTC One S is a nice phone, if you were to go for something new at this point then i'd say go for that. But I think it might be worth the wait until November when the new lineup of Nexus phones come out - that's approx 5 months away. I don't know how long you're willing to wait but it might be worth the wait.
It should be a month or two before we start hearing a lot more concrete evidence and not just rumours about these Nexus phones, and especially since the Asus Tablet will be running Jellybean, we'll also know what to expect for the Nexus phones in relation to JB.