So far, only Snowflake and Air Malta have announced low cost ops. to/from Malta. Snowflake will commence this summer schedule from Copenhagen and Oslo, whilst Air Malta will take on Stansted. Rumours of other operators are abound, but a strong rumour is Ryanair from Rome Ciampino.
Regarding Astraeus, they are presently contracted by the largest Maltese tour operator, which has already publicly declared it's intention of setting up it's own airline. Low cost with Astraeus could possibly be the first step.