The economy seating configuration is going to be 10 abreast according to the BA article in Airliner World. That's one pleasure I will not be looking forward to.
For the 787-8, I believe layout are all but confirmed as;
Club World
2-3-2
42 Seats
World Traveller +
2-3-2
51 Seats
World Traveller
2-4-2
90 Seats
A few other titbits,
The 777-300ERs when they come online will maintain 9 abreast as opposed to following the likes of EK and AF and offering high density 10 abreast.
First new 777-200ER for a few years, G-YMMR sitting in Everett.
http://paineairport.com/images/kpae4774.jpg
http://paineairport.com/images/kpae4771.jpg
Due to arrive in Cardiff for fitting out April 9th, and scheduled to be completed and sent to LHR on May 24th.