Hello Boicoilue53
As there are multiple Panorama Express trains in Switzerland, I wish to add that you are talking about the Gotthard Panorama Express (GoPEx).
Yes, this train does only operate in summer time, so do the steam wheelers on Lake Lucerne.
You could use the IR 26 train instead (named Treno Gottardo), it goes from Lucerne to Bellinzona and Locarno and operates on exactly the same panorama line as the GoPEx, with the only difference that the Treno Gottardo is to serve the locals while the GoPEx is a tourist train requiring 1st class tickets and reservation.
You can find all train schedules here: https://www.sbb.ch/en
Best regards,
Roland