Well it seems that Onkyo is replacing all its receivers - already done so replacing the 605 with the 606. ÿThe 875 was released in July 2007 - so I suspect it is going to be replaced by the 876 very shortly although this is purely speculation at this point but makes sense based on their history of product launches.
It's not speculation at all, the new 876 is due in the autumn. I would post the news item from WHF here but it was from before the site update and I can't find it now!