The center of gravity of the aviation world is somewhere in the ME right now according to IATA. They expect it to shift it even further eastwards simply based on population growth and economic growth around the world.

BA will not win the majority of the traffic and I think they know that. Best they can do are strategic partnerships and JV with airlines such as QR.

Of course, TATL is still very profitable and BA has a fortress hub at Europe's most valuable O&D airport.

I believe the aging of society we are seeing in Europe or Japan will happen in the US as well. It was immigration which postponed it for the US. But sentiment on immigration has very much shifted and I think the US will not welcome the kind of immigrants which statistically have many children going forward. Over the very long run (thinking a decade or two), there will be much less growth possible in TATL flying.

Who knows what kind of eruptions will emerge out of environmental concerns or from a tech company starting their own airline?

I'm not very clued up about the long run but from the few bits I know and talked about above, I would guess BA will try to grow in TATL markets. That can be through growth of the entire market medium term. Longer term, they will probably have to try to take away market share from others in very much saturated market.