Just when you thought that sedans were an endangered species, Automotive News reports that Cadillac will invest $175 million in Michigan assembly plant upgrades to manufacturer two new generation four-door sedans. GM apparently has already begun installing tooling for the new cars at the Lansing Grand River Assembly Plant which now builds the compact ATS and midsize CTS sedans. The two sedans, expected to be named CT4 and CT5, will replace ATS and CTS, as well as the XTS. The first new car, the CT5, will begin production next year with the CT4 following a short time later. The new cars may have some of the dynamic design flavor of the Cadillac Escala concept pictured here. The two sedans are part of a major overhaul for cars and SUVs at the brand which will also include at least two new crossover utilities.