It is also possible that Banner becomes stuck in his human form similar to how he was stuck in the Hulk form.
This is why I think that it is Bruce Banner, and not Tony Stark, who is piloting the Hulkbuster armor seen in Wakanda in the trailers.
What that means for the character in Infinity War remains to be seen, but what is especially interesting is that we actually haven’t seen a lot of Hulk in the trailers so far.