Cubs aren't punting on 2017 and 2018. Even if they gave up on 2017, they would need to get pitching for 2018 and beyond. The price for that pitching was likely to be Jimenez even in the off-season. And if they found a place to play Jimenez he wouldn't have made an impact until 2019.
My instant gut reaction was that it sucks to give up a top 10 prospect, but it makes sense given the Cubs needs and where they are at in their window of contention.