Actually Robert Lewandowski still have talented and enough for Bayern Munich next season, but he has try to leave Bayern before his contract ended next year, how ever make Bayern need to find new central forward replace with position leaving by Lewandowski. But Cristiano Ronaldo not as criteria for Bayern Munich depending have been on 37 years old, better looking for with young player and have chance to play with Bayern Munich about 4 until 5 years later. Not any special achievement if success with Bundesliga or domestic league only because Bayern Munich try how get top level and achievement on Champion League after failed last year.
Ronaldo is still quite able to compete there maybe 2 more years. In terms of age he is already below the best game, but the experience is truly extraordinary. Maybe his chances of winning the ULC are also open. Maybe it's not only the UCL target, but the arrival of Ronaldo can increase the income from selling their shirts. But actually the arrival of Mane was enough, if Lewandoski were to leave I think Mane would be good enough to replace him. With a note that Mane can immediately adapt to Bayern Munich's style of play.