Investigation is still going on. House Democrats have indicated they won't seat Harris unless and until it concludes with him being exonerated and the outcome not being in question as a result of McCrae Dowless's activities.
Most likely it will result in a special election since it definitely looks like election fraud occurred, but who the nominees will be (will the previous nominations still stand, meaning Harris will be the GOP nominee?) and when it will occur is still not clear. I guess they have to conclude the investigation before they even initiate the new election, which still may take months. And then if there's a new primary, the whole process for the new election will also take four months or something like that.
Probably nobody's getting seated until at least the fall.