Contend for a title, hell no. Will they make the playoffs? Definitely. If you think about it, who in the West has improved themselves as greatly as the Lakers have? You add the best player in the world, and you are going to see a dramatic improvement. There's no way that they can't. I'm not saying it in a prideful way, but just looking at the raw numbers.
Lebron is one of those guys who is like a high tide, in that he raises all the boats. If Lonzo keeps the pace going, and puts Lebron and his teammates in easier positions to get the ball and to score, then it will fall into place for him.
The Lakers purposely want to keep Lebron off the ball as much as possible, to save his energy for the season. Which means that his assist will go down, but all of his other stats could remain the same, or maybe even be a little better.