What you will need to do when you renew your TN visa at the border is to present a new offer letter with the Developer title with developer responsibilities. What the TN reviewer is looking for is to make sure your responsibilities matches your University/College degree. As long as your degree matches your new position, you'll get approved. In your case, it's not much of a stretch.
You'll probablyTN Immigration actually does not list every job combination and possibilities for all applicable fields. All CIS/IT jobs gets bundled up as "Computer Systems Analyst" IE: Quality Assurance Engineer, C#/Java/.Net Developer, Project Managers, IT Director, SQL Developer, Business Analyst, Systems Analyst, etc.
The only way you'll get denied is if you have a CS degree and now youthat does not match your new role. IE: You are nurse working in a Hospital for BlueCross. AND OR your offer letter is messed up and missing critical information.
Sources: I worked in the US with a TN visa from 2006 - 2010 until I got my green card and no longer needed it.