I know this is a late response, but we are on the cusp of attempting to solve this problem.
When doing this type of conversion what are you looking to retain and throw away. There are a lot of bad things that were done with InfoPath and we want to know just how users intend to use Nintex as the replacement.
I'm sure my team would love to see how we can help you achieve this conversion as easily and painlessly as possible.
I'm not the OP, but I found this thread because I believe I have the same question.
Essentially in my case I have a number of old InfoPath forms that I'm trying to recreate in Nintex.
Right now the current process is to painstakingly evaluate/reverse engineer each InfoPath form and build a new one from scratch in Nintex. There are often Nintex workflows attached to these IP forms as well.
Something we could point to the .xsn file in the old library that would automatically generate a new list and autocreate the fields based on the InfoPath form fields would be amazing. Similarly, if it could go one step further and see what workflows were associated with it and recreate those on the new list would be great.