I definitely think it could be fun, I would just be worrying that they would be overreaching themselves. My number 1 priority is always the single player

I think you mean.

Something like GTA 5 I wouldn't mind though....

I think it would've been a better game if they added a multiplayer more in Infamous than in a game like Uncharted... When I saw the first trailer of Second Son I thought a multiplayer would look a bit like Phantom Dust where you could use the environment at your advantage like launch a surprise attack from pipes and jump from roofs to roofs to attack, destroy the environment to kill other players etc... so am I the only one seeing this kind of potential for Infamous games?

I agree with your last sentence. 

I don't play multiplayer but I think Infamous has a real potential for some new innovative multiplayer fun.

Just imagine a huge open world map with a lot of players and each of them with different powers hunting each other. Very vertical gameplay and surprise alliances against tougher players.