Bryant is agnostic about whether the language of the Indus Valley script might be some early version of Sanskrit/Vedic. He thinks that the resolution of the question depends on a decipherment of the script.
By the way, I don't think any respectable scholar suggested that the language of Linear B was an earlier version of Greek before the Ventris-Chadwick decipherment proved that it was. So the Indus Valley script turning out to be Sanskrit would not be without parallel.