Lopez, with all his faults, is one of the elite postplayers, probably one of the top 2/3 low post players. Johnson might be perceived as not that good, but he is a multiple allstar for a reason and Williams is arguably the most complete pointguard in the league. I think this big three could be a very good match.
I think this team could be elite in the future, but next season i see them going 6-8 seed. They need some time to build their chemstry and learn how to play together. this situation can compare to the Heat's first year with the big three (yes they did make the finals but there was countless flaws that were perfected last season)