Gerry Adams will try to be elected as a TD in Louth. If he is, he will resign as an MP and an MLA. He took part in the Assembly proceedings, but was never an active MP as he never swore the Oath of Allegiance. Latterly he functioned as an MP from an office point of view, but in a fairly voiceless capacity. A by-election in West Belfast is unlikely to change this.
Ireland is in severe difficulties. I can't see much of Gerry Adams' political philosophy attracting the great and the good of Dublin society. This might be a wake-up call for them. Get your act together or face a revitalised Sinn Fein stomping around the Dail.