I really think Chris was very close to Avicii, being a slightly more old fashioned man I would imagine he would want to keep his feelings private. He must be devastated.
Personally think Nicky Romero should help Coldplay release Heaven as a tribute to Avicii. Would almost certainly be a certain Number 1 record worldwide, and raise some great money for a charity of their choice as well as be a fitting tribute. I'm a big EDM fan, have been for years. Nicky Romero is one of the best in the business, he would get it done right!