Airbus is potentially developing an A370. The information is from secondary and tertiary sources so it may be inaccurate – essentially a paper plane at this stage. It appears the 370 is a follow on to the 350.
The A370 appears to be targeted at Emirates and Singapore, to forestall 787 orders. Other airlines probably have been contacted. The information suggests Airbus will keep the current A350-800. The A370 would come in two sizes; approximately sized like the A350-900 and A340-600.
The A370 would feature an all new Al-Li fuselage with a ~236 inch (5.99m) cross-section that would allow 9-abreast seating in coach. This compares to the 5.28m cabin width on the current 330 and what is expected on the 350.