It shouldn't be much of a surprise that the Chorus gets the last word in Samson, since they've often been the voice of explanation or speculation in the poem. After Manoa describes just how lovely Samson's shrine will be, the Chorus suggests that things have turned out better than we expected. In the end, maybe it actually is possible to gain a sense of peace and calm from witnessing something dramatic tie up so neatly.
But many readers of Samson have seen this nice and simple ending as a little bit too nice and simple for a play that seemed to spend a lot of time thinking about suffering and complexity. And didn't we just read about Samson killing himself and a whole bunch of other people? Why would that ever be nice and simple?
It's safe to say that if you're feeling like something's fishy with this whole ending, you're in good company. Milton very well may have meant for his readers to arrive at a different conclusion than the one his Chorus provides.