We have at least 61 world heritage sites that represent Gothic Architecture
. The Basilica of Saint-Denis does look exquisite, and probably would have been inscribed if it was nominated between 1978 - 1996, when most of the major Western European cathedrals were inscribed. Twenty years have passed and the era of inscribing cathedrals, while certainly not impossible, has long run its course (particularly for Western Europe).
In other words, the ship has already sailed. France has moved on. In fact, the French Tentative List pre-2010 is largely exhausted. Future inscriptions from France, will almost exclusively come from the recent tentative list nominations.
*I included the planned WHC Evaluation year in BOLD
The Marquesas Islands (2010)2018
Chain of the Puys and fault of Limagne (2011)2018
Nimes, Antiquity to the Present (2012)
Volcanic and forest areas of Martinique (2014)2020
Metz Royal and Imperial, stakes of power, stylistic confrontations and urban identity (2014)2019
The D-Day Landing Beaches, Normandy, 1944 (2014)2018
Funerary Sites and Memorials of the First World War (West Front) (2014)2019
Great Spas of Europe (2014)
The French Southern Territories National Nature Reserve (2016)2019
The Alps of the Mediterranean (2017)
Nice, the new town born of tourism, or the invention of the Riviera (2017)
City of Carcassonne and its sentinel mountain castles (2017)
As you can see France has evolved in its approach to world heritage, its clear at this stage, serial nominations, transnational nominations, and overseas natural nominations
have precedence. As Solivagant mentioned, it would be unlikely a single cathedral would be put forward or inscribed. The balance of the world heritage list remains Eurocentric, particularly in regards to perceived over-representation of European cathedrals, castles/fortifications, and palaces. These views are well-documented here on this forum and similar views are often referenced by ICOMOS and the World Heritage Committee.