According to a recent tweet by @sleaknow (via SamMobile), it seems that Samsung could be planning a new virtual assistant. The tweet claims, “Samsung is developing a Virtual Assistant for its devices. It will build on S Voice app with search engine and clever notification.” Based on this, it sounds like Samsung will still be relying on S Voice to a certain extent.
Unfortunately apart from the rumored plans and how it will feature a better search engine, presumably to help look up information and whatnot, not much else is known about the feature and whether or not it will be hardware dependent, meaning that only new Samsung phones will get it, or if it will be available as an update so that older Samsung devices will get it.
Siri had similar hardware constraints where at the time of launch, it was only available on the iPhone 4S and older iPhone users were left out in the cold. In terms of launch, we can only assume that if the rumors are true, it will most likely make its debut alongside the Galaxy S7 which last we heard, could be launched in either January or February 2016.