I do think Apple are working on it, even if it won't be ready yet. They have a tendency to put a feature in a one product, like Touch ID was in the iPhone 5S and then move it to others, like the iPad and now the new MacBook Pro's.
I do not think Apple will implement the touchbar in the IMac. The main attraction of the IMac is its large screen, everything revolves around it, and the introduction of a small screen oled on the keyboard is totally unnecessary. The desktop of the IMac is so large and broad that it's not necessary to move certain shortcuts or buttons to the magic keyboard, also shortening battery life.
Rather, I think that the touchbar is a long way that Apple has started and that will end in a hybrid between IPad Pro and MacBook, becoming a unique product. If we consider the current abandonment to the desktop Macs, we could also think that Apple is directing all their research and development towards that hybrid and not to the classic computers.
So I don't expect a great update of the IMac which is different from a typical update of cpu, gpu, storage and ram (soldered to the motherboard of course).