BA stopped using the Galleries branding for new lounge openings in 2013 with the opening of the refurbished GLA lounge.
The GLA lounge, and all new and refurbished lounges up to the FCO lounge featured the Galleries Evolution concept (an evolution of the original Galleries concept), with lounges branded simply as 'British Airways Lounge'. FCO and ABZ have heralded a new, much smarter (IMO) concept.
The trend since 2013 has definitely been to combine First and Club lounges; take SIN, IAD and BOS as prime examples, with EWR before that. However, BA are still keen to differentiate at focus cities with dedicated F-only products such as Concorde Dining and Concorde Bar.
Separate First lounges will still be a feature at major hubs - LGW has a separate First lounge, as will JFK once the current refurbishment is complete later this year. I don't see any future where LHR loses a separate First lounge.
I would bet good money that the JNB, SFO and ORD lounges will lose a separate First lounge when they are refurbished, with the first two perhaps featuring a Concorde Bar product and the latter a Concorde Dining product.