Healthy ankle or not, I wouldn't hold out hope of him coming back later, 1) it's not going to happen, 2) he'll be that much older and father time has an unbeaten record. While his was never the quickest player, he still needed enough quickness to be effective....that simply declines over time, as well as stickhandling and reflexes. Some players are built to play longer while others are not....can be simply based on the player themselves, but there's also a lot to the type of game the player has played. Take Jagr for example....he's a big guy, lots of reach, wasn't good because of his speed, he was good because of his size and skill (rare combination). Again, while speed wasn't the most important, slow foot speed hurts everyone. He's not great 5 on 5 anymore and certainly isn't very effective in playoffs anymore.
Could Datysuk still be effective in certain situations? Sure, but too much to expect he'll be able to play an all around game....but again, the most important thing to remember is....there's no chance of him coming back, so no point worrying about it
The Pavel Datsyuk of 2016 was not the Pavel Datsyuk of 2007, and the Pavel Datsyuk of 2018 wouldn't be any better.
It was time for him to move on - and I'm actually grateful we didn't spend the next 3 years watching the inevitable sharp decline in a once game changing talent... But I'll never be convinced it was handled appropriately, and for that reason - I doubt the Wings would take him back.