This actually makes a heck of a lot more sense. It would have been pretty dumb of him to sign an extension with a team, since he would be leaving a lot of guaranteed money on the table that he could get by waiting until the end of the year.
This was the exact same thing we went through with Chris Paul and Deron Williams. They said they wouldn't sign and extension when they were traded, because an extension is for much less money than they could get by waiting until the contract expires, and they sign a Bird Rights contract.
And honestly, I think any team expecting Howard to sign an extension right now, is asking for way too much. The best they can hope to get is an assurance from Howard that he will consider them in the offseason. And since they will be able to offer him much more money than any other team at that point, they would have the inside track.