-Diggle will get a costume of some sort to conceal his identity. I suggested a Baklava but it will be more elaborate than that.
-Colton Haynes/Roy should be the character who moves around from show to show and is the link between The Flash, Arrow and Legends of Tomorrow.
-Lyla has a lot of secrets. She will end up as the head of Argus when Amanda Waller gets killed.
-Oliver will have a mole in Starling City telling him about what is going on with the rest of his team (Diggle, Speedy, Black Canary) while hes away with Felicity. The mole could be in his team but its not Diggle apparently. Personally, my money is on Lyla but who knows
-Felicity might get bored before Oliver of the domestic life, according to EBR. She found her calling with Team Arrow and eventually it will get tough for her to stay away from saving people. Thats how EBR feels, its not really a spoiler but it rings so true to her character I included it here. Thats also exactly how I feel.
http://olicityalamode.tumblr.com/post/120953177195/shc-paris-con-spoilers-edition