After having done a full release plan with multiple sprints it is not possible to change the order of the sprints in Plan mode. This makes it difficult to create sprints ahead and then change the orders around based on priority changes in the backlog. Sometimes priority changes would result in not just moving individual stories between sprints but changing the sprints around completely. This is currently not possible. Also if you have created several sprints and needs to add sprints in the middle due to time consumption higher than expected you can not do that either.