(1) Milwaukee should be able to win 20+ games just by getting Larry Sanders back. I do not think Jabari Parker will help his team much his first year out. He has too many problems in his game to overcome -- terrible defense, bad shot selection, inefficient scorer, bad decision maker = large number of bad plays that hurt his team and will negate the large number of good plays he will make -- So I expect Jabari Parker will be one of the weaker starting SFs in the league next year despite his gaudy ppg numbers. An empty stats player.
(2) Yes, of course. Kevin Love only 25 years old and Kyrie Irving only 22 years old. They still have a fantastic future there and a long window to compete for Championships because of the youth of those two stars. So both an immediate title contender and a long lasting title contender. It's not like the traded away Wiggins for 30+ year old player and only have 3-4 year run at this. This Cleveland team has a long window of opportunity.
(3) Wiggins will be better than Parker because of his defense and because he won't force too many shots that he shouldn't take. That said, he doesn't have the offensive skill to be a go-to guy and is more likely to be a role player level scorer + as a rookie, more likely to be a solid to good defender than a top defensive player. So while Wiggins will help his team more, that help is still on the fairly small side. I do think Minnesota can win 30+ games next year but it will be because of Wiggins' teammates (Pekovic, Thad Young, Rubio) rather than Wiggins himself.
(4) I do not think Wiggins will reach Kobe Bryant levels. I do not think his ball-handling and scoring repertoire is advanced enough to reach that level. I Wiggins' ceiling is closer to Paul George levels.