In 1.9.0 changelogs it was stated Missile explosion range is scaling more organically now, and that it doesn't cap.
However, the Explosion Range cap on Missile is still easily reached on Endless, at XP level 41 it reaches 3.2 and caps out.

Since this is a Missile thread I will also add that it is quite weak so far into the season, being a less effective damage stick than Tesla and/or Splash, and generally lacking a use case, in part due to its Special and Ultimate being obsolete with Gauss as a consideration.