What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
We don't have any concrete answer yet whether V3 will cease to exist on February 1, but you can always toggle your Form Builder version inside your account.
Seeing that this is an option located within your account (and not through the Form Builder itself), I think it's safe to say that this will be retained even after the V4 release on Feb 1.