Suero and Rainey have options, so if they don't make the team neither they'll just go to Fresno. That said, both have pitched decently this year. Strickland should be non-tendered as he's not coming back. Elias, he seemed to not be able to get lefties out, which is bad for a lefty reliever.
The Nats have left spring training with a bad bullpen for many years now. I don't know if that will be any different 6 months from now. With Voth, Ross and Fedde in the fight for the number 5 spot next year, I would put the other two in the bullpen. Having guys who can start in the bullpen worked for 120 years, it's only been the last 20 where relievers are specialized and starters either break with the big league team or go to AAA.
I'll assume Koda Glover will never pitch in the majors again, so I think they'll release him. None of the randos from this year, like Vetters, are coming back. Rodney, he'll be 43 and isn't that good, so I don't think they'll resign him. Did Grace accept a job at AAA? He got screwed over, getting DFA'd right as rosters expanded.