Either Syriza manages to get Greece in a better state after a few months, or it fails. Considering the first case, the "movement" will probably expand to countries that know austerity (Spain, France, and the likes ...), and coalitions will be formed to reach the head of state, and do the same thing, thanks to the spark from Syriza.
If Syriza fails ... well, nothing will happen mostly. I find the first way interesting actually, I truly hope they change Greece, and Europe at some extent.