The premise does sound an awful lot like Hook, but at least the world of Winnie the Pooh doesn't really lend itself to the kind of bloated excess that film was guilty of, potentially sparing us of another messy production. Mark Forster is a big red flag, though: that guy has done a great job of failing upwards, and it is a little surprising that he's still getting big films even after how much everyone hated his guts on World War Z. Money talks and bullshit walks, I suppose.
There's a biopic coming later this year that centers around the relationship that AA Milne had with the real life Christopher Robin, but I expect that's probably going to be the usual gentle biopic template to a T.