Doesn't, "Believe It!" In the English dub Translate to " Dattebayo" in Japenese? He hasn't said Dattebayo recently but I'm sure I've heard him say it in shippuden.
Dattebayo or -ttebayo or 'ttebayo was translated to "believe it", but I think it's more closely translated to Ya' know, like Kushina's Dattebane, -ttebane, 'ttebane. So further down the line if I'm not mistaken he says that now. I dunno, but that was irritating af.