Maintenance for the week of April 6:
• [COMPLETE] ESO Store and Account System for maintenance – April 8, 9:00AM EDT (13:00 UTC) - 6:00PM EDT (22:00 UTC)
That's a good question, though I want to go ahead and say no (mind you I don't know 100%). Considering that some people have canceled their subscription already to prevent the auto charge, and they still post up, I'm going to say no.
The forums are supposed to only be for people with an active subscription. If there's an issue with people who cancelled still posting, it's probably due to the free month.