This NHK document lists their upcoming shows and Card Captor Sakura Clear Card TV Anime appears on page 13 with a total of 26 episodes scheduled.
If the anime runs for 26 weeks without interruptions, the 26th episode would air in early July, summer in Japan, the perfect time for a theatrical movie release. But that is only speculation of my part.
It’s unlikely that the manga will be over by then, which makes me think that there will be at least another season.
Thank you to Sakura84-chan for the heads up!