Now we all know Marvel are building everything to the Infinity Wars Parts 1 and 2 but have the seeds for the next phase after that been planted under our nose since the first season of Agents of S.H.I.E.L.D?
Let me explain in season 2 we discover both Skye and Raina are due to become Inhumans, and now flash back to season 1 episode 3 "The Asset" Dr. Franklin Hall has been kidnapped. Coulson and his team are assigned to rescue him. The final scene of this episode is a shot of a hand flying out of the Gravitonium.
Now I can see two links to M.C.U with this, at a guess i would say this was the birth of Graviton a man that can control gravity. According to Wikipeidea his first appearance saw him taking on the avengers and almost destroying them if the Black Panther had not escaped to summon Thor he would have accomplished his goal. So could this be a link to Ragnarok or is it option two? His second appearance saw him up against the Fantastic Four and non-other than Black Bolt the leader of the Inhumans seems a little bit of a coincidence that we are seeing all these Inhumans being introduced in the same programme.