While I agree Hronek has likely earned a call up at some point after Green is dealt, I doubt they do anything to specifically open space for him. I would however imagine that if he has a good camp/preseason next year, he could make Ouellet or Jensen expendable enough to waive or trade. Obviously, he'll wear a different number than #13 on the big club. They probably just toss him #4.
As for Fedorov and Datsyuk, both departures offered a silver lining, so trying to rank which was worse is moot.
IMO, Datsyuks departure seemed to have more to do with money than his daughter. If you read Ken Daniels "If These Walls Could Talk", there's a part in the book about Daniels sitting next to Datsyuk on the plane during his last season and listening to Pavel complain about how much the players contribution to escrow was rising. Considering escrow hit as high as 18% in 15/16, and his salary for 16/17 was to drop down to $5.5M, after taxes and escrow, he was probably looking at making a good bit less than he signed for in the KHL for this and last season. That said, the Wings were at least able to salvage another D prospect out the whole thing, so unless Chychrun wins some Norris trophies and/or Hronek and Cholowski become the next Kindl and Smith, the Red Wings made out fine.
As for Fedorov, his departure ended up being a blessing in disguise... Had he signed one of the Red Wings $10M/season offers, the Red Wings would have faced coming into the cap era with Fedorov and Lidstrom occupying a hair under 40% of the $39M cap... They would've had to do a lot more trimming other than Hatcher/McCarty/etc., and one of the casualties could've been having to trade Datsyuk or lose him to the RSL, since they barely got him to sign for 05/06 in reality. I also wonder how Red Wings fans would've viewed Fedorov had he stayed with Detroit and his game dropped off like it did post lockout with his cap hit either 2nd highest or tied for highest. Especially when you consider that by having to adjust to carry Fedorov's likely high cap hit, the team more than likely wouldn't have been as deep and talented as they eventually were for the first few seasons out of the lockout. Then again, the Wings probably don't trade for Lang if they keep Fedorov, so they potentially still have a 1st rounder in 2004 (which was used by Washington on Mike Green) and Fleischmann, and whatever they might have gotten having to trade somewhat to get cap compliant.
#13 and #91 should still hang from the LCA ceiling someday, IMO.