I have assisted / seen a number of customers upgrade their TH3030S from 2.x to 4.x with success. Regardless of the platform, there are some significant changes within the ACOS CLI and API which occur during the upgrade. An automated upgrade script will run on first boot of 4.x code and will convert the configuration. Most of the time, this is a very successful process, but it is important to check the config afterward. A 2.x to 4.x upgrade guide is included in all the latest 4.1.4 documentation files.
Another pre-validation option you can explore is backing up your configuration, and restoring the config into a virtual thunder in a lab environment.