1..You would have to find the blanks for your existing car if you took the bolts out of the rails and removed rails.
2...Do you know that your next Ecosport will have or not have roof rail? (dependent on trim bought)
3...Genuine Roof rail kit for Ecosport is around £130 at today's prices. (not including cross rails).
4...Think I would worry about it more, when you decide to change cars.
PS......Do not think anyone will have the answer to the above, but easy way to check, is measure up your own car, and go into a dealership with a tape rule and measure up against a new Ecosport. Sorted