Depends what the filler is. It could end up being interesting if they're flashbacks to juxtapose Lois and Clark now versus when they had small children or even learned Lois was pregnant. While it wouldn't mess with the arc narrative, it could flesh out the characters and their journey.
I'm looking for a silver lining because this means that it's filler or they had an unsatisfying ending that they only barely managed to pull together because they got given two more episodes. Time will tell. Filler or no, I just want quality.