So we have at least these combinations to speculate on:
- John Williams travels to London to score the film with LSO
- The LSO is brought to US to score the film (JW conducts)
- John Williams scores the film at US with a studio orchestra
- The score is recorded at London by the LSO with someone else conducting and Williams supervising the process
And while the sound of one symphony orchestra might not be readily distinguishable from another to most people, I am sure all the people involved, including LSO, would like to continue their association with this franschise.
Perhaps another option would be for John Williams to conduct a renowned American orchestra in the US, like using the Chicago Symphony Orchestra for Lincoln instead of a studio orchestra. If that is the case, my bet is the BSO given his relationship and history with them.
Obviously, my preference is a LSO conducted score though.