You're right, the issue with that curve is further downstream, where the two lanes from Santa Fe and the four from I-25 get crunched into only three through lanes in the section that goes from Alameda to 6th Ave. It's on the list of things for CDOT to fix, but like so many others it depends on funding they don't have yet. One of the reasons it's such a pain is they have to basically pick up the consolidated main line tracks and move them a couple hundred feet east (which isn't easy when you have multiple trains going through there every day). 

The full EIS they did for the whole project is here: https://www.codot.gov/library/studies/i-25-valley-highway-EIS