Odia is more likely to go HD sooner than Assamese. Odia has more channels, which are from big national networks, and a larger population. Star Kirano HD is officially on the cards and Zee Sarthak HD and Tarang HD should hopefully follow after that.
That said, there is nothing stopping an Assamese, Gujarati or Punjabi channel from launching an HD version (especially since Fastway Cable already has several exclusive Punjabi and Hindi HD channels).