Researching with someone as a stopgap
If you came to me and said upfront that you wanted to get research experience and wanted to work with a variety of professors rather than making a full commitment to only one, I would try to find a way to accommodate you. 

Or at least I would let you know what my expectations are. But, in any case, we have an honest relationship. 

Now there would be no question of an ethical bind if you later decide to work with a more prestigious professor. 

But the honest relationship is very valuable given that the professors know one another and you don't want to get caught in a bind between two professors.