Temp DB space allocated- will it be reclaimed ever?
Like all databases, free (unallocated) space in tempdb is reused for new objects.  No action is needed for this space to be reused.  

The physical size of tempdb files will reflect the high-water mark of growth since the instance was last started.  The size will revert back to the initial file size after an instance restart, freeing space on the disk volume if growth occurred.  It is also possible to release unused file space using DBCC SHRINKFILE.  That should not be done routinely but may be desirable if the growth was an anomaly, such as due to a bad query.  It is best to size files to accommodate expected space requirements and provide growth as a safety net for unexpected needs.

Multiple tempdb data files of equal size and growth can improve performance by reducing allocation page contention for some workloads.  However, that is unrelated to space reclamation.