[Solved]-How to create Sankey Diagrams with curved node endpoints?-d3.js

Yes, it is possible (and relatively easily feasible) with d3.js.

Here is an example:

http://bl.ocks.org/cfergus/3921009

You will most likely need to adjust the code to suit your need, but this is basically a solution to your problem.

Take a look at this random Sankey generator:

http://bl.ocks.org/cfergus/3956043

After a while you'll get graphs with loops.