One would think that a straight cityname.com, would always remain valuable.
The interesting twist is if the citystarts being offered as an extension. If ".coventry" options became available, a business might be inclined to register their specific focus for the domain name. For example, tourism.coventry could have some significant appeal, as an alternative to a presumably much pricier coventry.com.
If you're just investing in CityName.com then idk but if it is CityNameProduct.com or CityNameService.com then you will definitely get a lot of potential buyers. Albeit you'll have to do outbound.