Former President/Presidential Nominee on the Supreme Court?

[Skill and Chance]

It happened twice in the 20th century, does anyone think it will happen again in the next couple of decades? 

Obama will still be pretty young into the 2020's, although I'd imagine the next D president would need a huge senate majority to get him through, particularly if it's the 2016-2020 term. 

Rubio would also be an enticing possibility for many reasons.

[Talleyrand]

No, he would have too many conflicts to take on the job, even if the hypothetical D President had an immense senate majority. Also, he'd be at least sixty. The goal these days for both conservatives and liberals is to nominate an ideologue in good health no older than 60, and that age is pushing it too.