When you practise regularly you will progress. To what extend and in what direction depends on what you are working on and what gets presented in class.
In my experience this progress does not relate to strongly to a grade. However, when training for the next grade it sometimes happens that you 'get' something that you until then did not understand. But I think this is a result of more intense training rather than the specific grade you were preparing for.
Also you yourself may, and probably will, change during your Aikido 'career', so comparision of how you progress at higher grades and your progression at lower ones is hard, if not to say impossible.
I have changed considerably since I began Aikido. Focus has shifted from me learning the techniques to how to pass the knowledge on to (my) students. What connects techniques? What is a good way to safely have students practise ukemi? That sort of thing.
When I started out I saw mainly differences, today I see similarity.