What is the best approach to re-awarding the task order to the current incumbent?
In order to remove a requirement from the 8(a) program, you must get approval from the SBA. Paragraph IV, B, 25 on page 8 of the SBA/DoD Partnership agreement (https://www.sba.gov/sites/default/files/files/Department of Defense.pdf
"a Contracting Officer shall notify SBA in writing of their request to release a requirement from the 8(a) BD Program. The written notification should be sent to the cognizant SBA district office serving the geographical area in which the procuring agency is located. The Contracting Officer shall include the reason(s) for the request, the procurement history of the requirement, the incumbent name, the assigned NAJCS Code and the Statement of Work. The final decision rests with the AA/BD;"
If you are within the FAR 19.805 dollar thresholds for 8(a) sole source and your firm is still in the 8(a) program, you can offer the requirement to the SBA in order to keep your incumbent. If not, then you must find another 8(a) firm. If the requirement is over the 19.805 dollar thresholds, then you must compete the requirement within the 8(a) program if you have a reasonable expectation that 2 or more firms that will submit an offer.
Check the SBA/DoD Partnership Agreement and FAR 19.8 for more information.