What’s the next city to get an RER/Crossrail line?

Thameslink wouldn’t count as that’s more like an S-Bahn. An RER/Crossrail system has a long central section which is about as long as the cities metro line it parallels.

Thameslink wouldn’t count as that’s more like an S-Bahn. An RER/Crossrail system has a long central section which is about as long as the cities metro line it parallels.