Snap will never dare to return to Hogwarts. He will go with Wormtail to Voldemort. Draco will return to his mother. Voldemort will be angry with Draco but I think he will be so pleased with Snap. He will trust him more and more. Bella won't love that, i suppose.
Until now there are different opinions about Snap being good or bad so What he will do is he will join Voldemort and help him if he is really bad or he will join him and play a secert role form the OOTP. Who knows??