Porsche is calling the Panamera a "four-door coupe," though the automotive media generally seems more aligned with classifying it as a "mid-size luxury car." I agree about the sporting aspect, but given the price range and overall design, the Panamera is likely to end up at least somewhat competing against Audi, BMW, Mercedes, etc. luxury sedans for consumers' buying dollars - especially if someone is interested in the up-market Panamera Turbo model.
Anyway, some hardcore Porsche brand purists will probably decry the Panamera, but many broad market Porsche enthusiasts and brand newcomers will probably still buy it. It is basically the same market concern that occurred when Porsche launched the 928 and Cayenne models.