FAQ

There's a possiblity that the two future episodes of Ben 10 was an alternate future and with the new addition of this show that future has changed. Or maybe, if they ever end this show, they'll have a falling out after a huge argument, and Kevin will run away and plot future Ben's downfall because another theory is that he might still become evil, in the future it shows he was locked up in the Null Void but the last time he was sent to the Null Void was when he was eleven, he could'nt have stayed in there until the events of the future because he has a ten year old son named Devlin so during the time between Ben 10 and Ben 10: Alien Force, he somehow got out and started dealing in Alien tech that led to the events in Alien Force where he befriended Ben but somehow in the future, Kevin might go back to hating Ben like he did when he was eleven forcing Ben to send him to the Null Void.

Yes. he will appear in the session three opening and may appear every so often afterwords.