Maybe, kind of. LearnDash stores your students as users in the WordPress system. If you stick with a WordPress solution, your users will remain part of your site. You will still have to do some work to enroll them into the courses on your new system, but there are some bulk editing options for that. If you switch to a hosted/SaaS LMS, there are no direct migration tools I'm aware of. You'll need to export your users from LearnDash to a .csv file, and then see if the new platform allows for uploading in bulk. Some will, some won't.