Given First's ongoing efforts to standardise their fleets, will the Geminis at Hadleigh eventually bow out and leave?
I cannot imagine they will remain long-term - but something has to replace them.
Current standardisation efforts are concentrated (mostly) on South West, West & Wales and Worcester - Worcester and Wales are swapping Euro 6 StreetLites for Euro 5 Enviro 200/300s (StreetLites to Wales, Enviros the other way), while South West are gaining B9TLs from elsewhere (East Anglia, West Yorkshire and South Yorkshire) to rid themselves of their remaining elderly B7TLs (most of the B9TLs being released by the arrival of ex-Hampshire, 22-reg StreetLites themselves replaced by the electric fleet at Hoeford). As for West, there is a big shuffle going on there to put Enviro 400 MMCs at Wells, Scanias/B9TLs move to Bristol and Bath gains "classic" Enviro 400s. That said, Colchester are also getting Enviro 400s from within the group to replace their remaining B7TLs too.
I suspect any remaining Hadleigh standardisation will happen next year, when the new Yutong fleet arrives at Basildon and releases a lot of Enviro 400s.