Agreed; heck look at what Punk's sudden departure from the company did for the company and for Daniel Bryan when it came down to their WM 30 plans.
Now provided that the Rock isn't brought back to main event WM 31, this could be good news for Dean Ambrose since he's likely to become the next candidate in a situation like this that the company will focus in trying to build upon.
I think it would be better if Reigns just ends up taking on Triple H for WM 31, with Ambrose and Daniel Bryan being involved in a triple threat match involving Brock Lesnar.
Personally, this is how I would end up booking WM 31:
1. Daniel Bryan vs Dean Ambrose vs Brock Lesnar (WWE World Heavyweight Championship Match- Triple Threat). Let's say that John Cena helps Ambrose screw over Rollins into losing his Money in the Bank Contract to Ambrose himself. Daniel Bryan returns to the Rumble where he wins it and Ambrose ends up cashing the contract in advance for a WM 31 Match.
2. Roman Reigns vs Triple H
3. John Cena vs Seth Rollins... which is a result of the scenario listed above.
4. Bray Wyatt vs Bad News Barrett (Intercontinental Championship Match)
5. Cesaro vs Dolph Ziggler vs Sheamus vs Kofi Kingston (US Championship Match- Fatal Fourway)
6. The Undertaker vs Sting (Retirement Match for both Wrestlers)
7. The Usos vs Stardust and Goldust vs The Colons (Carlito and Primo back to their original gimmick) in a Triple Threat "Family Feud" Match for the WWE Tag Team Championship.