Congress is considering many bills to alter election laws this year. One of them, the Military and Overseas Voter Empowerment Act, is likely to advance on October 8. The Act requires the states to mail absentee overseas ballots at least 45 days prior to any federal election. It is part of S.1390, the Defense Authorization Bill, and has already been passed by the Senate.
The House version of the Defense Authorization Bill does not include the Voter Empowerment Act, so a conference committee will decide whether the Voter Empowerment Act remains in the bill. That conference committee will be held on October 8. Most observers expect the conference committee to retain the election provision.
Assuming the bill is signed into law, it is almost a certainly that the states that now use September primaries for Congressional elections will be forced to move those primaries into August, or an earlier month.