Wed & Thurs (triple episode) spoilers have been added to the original post.
It is being reported that Harper & Dana's mother, Kerrie Matheson will be arriving in SB in the coming months. This character will be played by actress Sara Wiseman (confirmed by her CV). Sara previously starred in A Place to Call Home, Shortland Street and High Country.
Stephen Madsen has joined the show as character Eddie Shepherd (confirmed by his CV), whilst it is believed that Lach Millar has been seen filming at Palm Beach playing a new character (Lach previously played character Richie Amblin in Neighbours). There is no information about these characters as yet, nor whether they are guest stars or regulars etc.
Also, a couple of months ago a large number of the H&A cast were seen by residents of Cowra filming a number of scenes at the Lachlan Valley Railway Heritage Centre (Cowra is a town in the Central West region of New South Wales, about 4 hours from Sydney). Nothing has been confirmed, but the filming made around various train yards has prompted fans to speculate that some kind of train crash may feature in this year's H&A season finale in Aust. We will see...