I really don't know about staggs. He tries really hard I will give him that, but he doesn't have much Xfactor to his game. He isn't overly big or fast.
Im fairly certain Oates and TPJ will stay. Im less confident we will retain Offa. He just never seems to have a huge breakout, and I'd suggest that there is more upside to people like TPJ, Carrigan, Flegler, Lodge, Haas, Fifita, Sua etc so of the forwards he would probably be one to miss out on a renewal. Considering Offa also likely would demand more than Glenn, I'd take Glenn just for the better leadership he offers and the pure consistency in his performances.
I imagine our 2020 side to he something like this.
1. Boyd (unless we get a replacement)
2. Oates
3. Roberts / Staggs if he leaves
4. Bird
5. Isaako
6. Milford
7. Dearden
8. Haas
9. Macca
10. Lodge
11. Glenn / Fifita if Glenn not renewed
12. Gillett
13. TPJ
14. Nikorima
15. Flegler
16. Fifita
17. Carrigan / Sua