If a new medium emerges like the Internet years ago, can I decide what I want to do with my work in that respect?

If as the author of a work, you assign all copyright to another party, this includes all future forms of exploitation. In that case, you can no longer decide what you do with your work.
If you partially assigned your copyrights or granted a licence, it must at least be contractually established that the party to which you assigned the copyrights or granted a licence is also entitled to engage in any future forms of exploitation. In that case, how much leeway you have to decide what to do with your own work depends on such arrangements. Also check the copyright contract law that came into force on 1 July 2015 (amendments to the Dutch Copyright Act) and see whether this applies to your situation.