Since you are on SQL 2012, new Windowing Functionality is available too. Here is a solution based on that. Note you may want to add in columns and/or handle missing endpoint(s).

;WITH a AS (SELECT datestamp AS datestart, currentstatus, lead(datestamp,2) OVER(ORDER BY datestamp) AS dateend

FROM @test-2)

SELECT DATEDIFF(dd, datestart, dateend) AS dateinterval

FROM a

WHERE currentstatus = 8

AND dateend IS NOT NULL