I'd say that Hindu/Indian beliefs definitely trace back to an early Indus Valley culture. There's a lot of similarities between Avestan/Vedic language and religion. Too many similarities for them not to be related. There's a continuity there but also huge breaks in continuity too. I mean, even from Vedic to modern Hindu religions there is a huge break, much like the break between Judaism and Christianity. There's some continuity and influence but also very huge differences that make it hard to argue that the latter is truly a perfect continuation of the former.