Its unlikely they would order 4 744 after they just dumped off two barely used 747-300's.
A318? Unlikely. Swissair generally use their partner Crossair on thinner routes employing a variety or regional aircraft like the Saab 340, Saab 2000, Avro RJ 85, and RJ 100. A318 is designed for very long thin routes and the distances involved (intra-Europe) don't merit such a heavy aircraft. Most likely SR will rely on Crossair's new ERJ 170/190 to take up the slack in this market while keeping the lucrative stuff for themselves while allowing Crossair to provide feeder service.
Luckily for SR, they don't have pilot unions like they do in the US which use incredible pressure to keep regional jets below the 50 seat mark. This is going to allow great flexibility for SR/LX but creates an uncertain future for the new class of bigger regional jets within the US.
Hope this helps.