If you mean the church, it won't close as it is still in use as a church. The vaults bring in some revenue from tours so I doubt they will be closed either. These lovely historic churches still retain small but loyal congregations. It was a regretful decision when the CoI closed St. Mary's in Mary Street and St. Paul's in N. King Street. But that was then, and this is now. Property is viewed differently now.
Surely the reasons the CoI churches were closed in the past will be the reasons they will close in the future? What's changed in how property is viewed nowadays? I would imagine it's all down to costs of upkeep and the size of the congregation. Did St Thomas' not close recently?