Yes Tom. All the old data will be kept !
As 1.6.1 changes the name of menu parameters from category_id to id, from event_id to id so if you created any menu items to link to category view or event detail view of Events Booking, you will need to make sure you edit these menu items, make sure you select the correct category/event.
After that, everything will work as expected !
Regards,
Tuan