Denmark barely controls Greenland today as it is. As with the Self-Government Act, it's most likely that Greenland will continue to gradually shift toward full independence.
If Greenland develops into anything, Denmark won't own or control it. For example if a million people move there over 50 years, perhaps seeking isolation or lower population density vs mainland Europe. It would be its own independent nation, not dissimilar from Iceland. The only way Denmark could hold onto Greenland would be through military action (never going to happen).