Upgrading CI to last version

No because some of the updates make changes to the ./application folder and perhaps to index.php.

I believe there is only one change in the ./application/ folder associated with moving to 3.02

Otherwise, simply replacing ./system with the most recent version will work just fine. BUT, it would be wise to walk through each of the Upgrading From a Previous Version docs and make sure to take care of the very few items that require additional actions. All that said, some of the items should be checked by a developer.