I am just trying this workflow currently and was wondering if it is possible to update the Revit model and just re-link to Blender after sending it.
Unfortunately, re-importing a model from Revit to Blender creates duplicate objects but the Speckle team is planning to fix this at some point according to this post: https://speckle.community/t/revit-to-blender-creates-duplicates-in-blender/8083/19