Would it be correct to assume that inner query ordering will follow into my outer query?
You cannot depend on any ordering unless you have ORDER BY in the outer query. The ordering will depend on the execution plan chosen.
In the case of the present query I cannot think of a reasonable execution plan that would not preserve the ordering, but who knows what the future will bring for the query optimizer?
I would write a second ORDER BY. Sorting 1000 rows is cheap, and you can be certain then.