Not sure I'd say zero chance. If Tanaka ever was going to buy into the cubs it had to be more for years 3-6 or 7 depending on the length of the deal. In that case what good is an opt out at year 4? Year 1 would have always been an adjustment period as their best prospects are only likely to see half a season tops. Year 2 would have been the first year of full time on Baez/Alcantara and possibly Bryant. Year 3 you might see Soler and Almora. So, in the fourth year you likely have all of the big guys up but at that point there's still an adjustment period for a lot of players.
Some players will be Longoria's and be what they are to start while other players are more like Chris Davis was who took 3-4 years before he finally reached his potential. Others will never. The point here being if you buy into the cubs you buy in for the length of the deal not just the first 4. Obviously he wasn't comfortable with that which is his choice and admittedly a fair one. However, I don't really think that's what cost the cubs him. What cost them was the fact that they aren't ready to compete year 1.