A naval maritime-patrol service would likely join the Orion programme

If the Royal Navy controlled maritime patrol, what would replace the Sunderland and its successors?

Probably a land-based aircraft, with the Royal Navy more likely to join the P-3 Orion programme than develop Nimrod.

Control by the Royal Navy would not necessarily preserve flying boats once a land-based aircraft offered better utility. A Shackleton-like interim path could lead to participation in the P-3 Orion programme instead of a uniquely British Nimrod development. Mission requirements would matter more than attachment to a particular airframe type.