We spent 6 days in the Cinque Terre last month (October), and it was quite different from our Amalfi visit a few years ago. It was also different from our previous CT stay, way back in June 2001. Now that it’s a National Park, with marked and somewhat maintained hiking trails, it was surprisingly busy. It was as if half of Germany, and all its hikers, were there, visiting for the day or longer. And we saw and heard more Americans there than anywhere else in Italy last month, including Rome. The sightseeing boats going between towns were full. Trains were not as crowded, but there were still plenty of passengers. The area clearly still has lots of allure.
We stayed in an apartment in Riomaggiore. Vernazza was packed, shoulder to shoulder. Restaurant reservations were needed for dinner many places. La Spezia was such a chaotic city to pass through, and not scenic, that I’m glad we stayed in one of the 5 towns. That also serves as a case if you wanted to explore more of the area. Due to storm damage a month earlier, the main walking trail between Vernazza and Monterosso was closed off. Since the other main inter-town trails have been closed for some time, only the Manarola-to-Corniglia main trail was open, along with secondary hiking trails, higher up and steeper/more difficult.
Can’t say what will be open or closed for you a year from now, but October was a decent time to be there. I’d have enjoyed it less in the hot, even busier summer.