if asked as a fan, I'd be against it. we came back to the 1st division easily, we got a good team, a good coach, and we can even try to grab the São Paulo State league or the National league title. there's no need for a big star who is virtually an ex-footballer.
on the other hand, Ronaldo is Ronaldo, and not only a Cronaldo. He's fat, drinks a lot, smokes, probably snorts some coke now and then, fucks some trannies and all, but he's still the second best striker ever after Romário, the top scorer of all world cups, a legend of football history.
if he decides to take it seriously and come back to form, he may be a good surprise for the next season.
edit:
according to Corinthains managers, he decided to play for Corinthians instead of small euro clubs like Man City, Villareal and the likes because he wants to play in the next world cup. if he becomes the leading star of one of the most popular teams of South America, he'll certainly get much more attention from Brazilian media then he would get playing in Europe. Thus he's giving up some millions to have a chance of coming back to the national team.