No!
No no no!
ET, under no cirucumstances, belongs to Lucas. Yes, there were the little ET critters in TPM during the meeting, but that's called a cameo appearance. ET is NOT a jedi, and doesn't belong in the Star Wars Universe.
With that said, for more practical reasons, ET being a jedi is plain stupid 😖
IMO, (although I know this wasn't the intent of the original film, this is strictly my own EU creation) E.T. WAS a Jedi. My reasoning? We see him display force powers, such as Force Heal, Telepathy, I think telekinesis as well but I can't remember. Secondly, when E.T. sees the kid in the Yoda costume, he goes "Home, home" and trots after him. But the crowning element is this:
When the astronaught comes to get E.T., he acts scared. But he doesn't act it when he sees the astronaught...only when he hears the astronaught's breathing just before he shows up. Breathing that sounds a lot like a certain Dark Lord of the Sith.
So yeah, in my own mind E.T. and his crew were on a desperate mission to escape the Empire, with a Jedi on board. Why else would they leave him behind and just take off like that?