My understanding talking to family is VDOT is looking to expand nearly all of I-81 in a series of projects ... now that could take 20+ years, and there will likely be some bottlenecks where 3 lanes merge to 2 at various stages. I'd guess 5 years or so perhaps for the HBurg segment.

Found a VDOT link to the overall master expansion plan for I81. They have a rough timeline, and looks like it extends out to around 2032 to expand around 90% or so of I81. There would still be some gaps/stretchs of 2 lanes, which could make traffic "interesting" - particularly in the stretch from Winchester to Harrisonburg.

https://improve81.org/