You can get promoted as long as the job duties (or in my case, area of expertise) stay the same. In my attorney's opinion, it is unrealistic to expect that a talented, qualified person would not be offered a promotion at some point in their career, and given the long processing times at the USCIS, it seems reasonable. Promotion often involved the added responsibility of managing people with your skill set, in addition to delivering work in your skill set too. A letter of clarification from your company regarding the promotion should be sufficient (same basic duties, just a higher level.)