In the Advanced Roadmaps for Jira Server, version 3.28.0 (formally known as Portfolio):
How can I show my plan vs. sprints in the timeline view? (instead of the time range dates; not as a column)
Sprints should include the active and planned sprints, as well as the virtual ones 'simulated' by portfolio, as we had in the legacy interface.
If I understand you correctly, this should add the sprints to the timeline view:
This shows me all the active and planned sprints with their names and adds "projected sprints" as needed.
What seems to be not available at the moment is to assign a sprint to a team. So if you have multiple teams/sprints running in parallel the layout is a bit messed up.