Motion Twin have announced that the upcoming Update 35 for Dead Cells will be the end, so it will be actually finished and complete with no more content updates.
They shared the news in a post on Steam saying that "Update 35 for Dead Cells marks the end of our creative journey on the game. After an incredible 5-year collaboration in bringing additional content to Dead Cells' live-ops, Evil Empire will be pursuing new adventures and we can't wait to see what they come up next.".
One of the issues noted is they didn't want to fall into the "more of the same" trap, as they didn't want to "overextend and risk diminishing the unique charm that makes Dead Cells special to us all". This is part of why things have been quieter around Dead Cells recently, as they said "concluding such a partnership required careful planning to ensure a smooth process for everyone, including the community" as Evil Empire and Motion Twin both move onto new things.
Probably the right move. Dead Cells as it is right now, with the multiple DLC released, is excellent and packed full of content to explore and fight through. Not everything needs to be expanded upon forever. There's currently no date for the final update yet though.