Unfortunately I do not have any news on the new Yamaha subwoofer, but being an owner of the Wharfedale SW150 for many years I can give a little insight to help you. That thing is a little monster, on paper it doesn't seem powerful and it isn't that powerful, but it's very precise and dynamic.
I've never had a listen to the Gemini II BK subwoofer, but judging by the
review it seems like it has a bigger boomy sound perfect for movies, but isn't so great for music. There's also the fact the Gemini is a downward firing sub - not ideal for a flat or a bedroom. IMO the Wharfedale is a better allrounder and that shows in the
review too, not to mention it's cheaper.
If I were you though I'd personally have a demo setup of the subs you want. If you live in the UK, the Hi-Fi retailer Superfi is a very good partner of Yamaha and may be able to get you a demo alongside the Wharfedale SW150 which they
sell.
Also, what is with people on here always refering to BK Electronics? I understand they may be good and well respected, but the OP didn't ask about that company. He specifically requested information on the subs in his thread title. I had the same thing in my sub thread too. The default answer shouldn't just be go to BK, that's just really unhelpful. Give help based on what the OP has requested first and then refer to something else as a "by the way, did you know this exists too?" kind of thing.