On your last point, if I thought that the only possible use for the rumoured Google Assistant headphones was as a device to play your music list, I would be more inclined to agree. However, I see voice assistance becoming much more than that. I see the headphone replacing the need to take the phone out of your pocket for an increasing number of things I do.......search, get directions, get timetables, shop, pay for things, make phone calls, send messages, etc. I know that there is a time and place for everything and it might not suit everyone to use voice activated headphones all the time. But the fact that I have the option would make these headphones extremely appealing to many people, in my opinion.
good god no, and same for shopping for a lot of that you simply need a screen. A quick glance at a map tell you so much more, than any verbal communications. Partially the same for timetable i would rather see a timetable and all the information than my headphones needing to talk to me for 5mins and then you still cant compare as its very hard to compare a lot of info in speech form, but extremely easy in visual form. However if its a regular route you know, and just want next bus time, then yes that could be good.
Same for shopping I cant ever see voice only shopping becoming main stream, visual comparison of images and information is so much faster. However it would be useful for a shopping list.
Ok google add garlic to ocado
or similar, then when you next fire up ocado website or app you see the shopping list and a click on it brings up a search for all garlic products.
I think people either over estimate how much you will do with voice, or under estimate, you can do a fair amount, but visual is still king for many things that people say you will do with voice.
it'll all change again when display contacts or glasses become mainstream, the combo would be extremely powerful.