If you were rotating to a grass next spring...... I could say kill now or wait.

But, when going to beans next spring, I would recommend killing now.   Alfalfa is a variety.... some will likely be dormant already, and a complete kill, even with 2-4D and or dicamba  now will probably not result in a complete kill, but will likely be mostly complete.  

Yes, RR alfalfa presents some new challenges.  

Tillage can do a pretty good job, but if the field presents erosion concerns, tillage may or may not be a good option

Most likely, attempting to kill the stand now or soon, with 2-4d and or dicamba,  would be the best option, imo.