If you say it in context, you will probably say "em breve". See you soon = Vejo você em breve I'll finish working soon = Vou terminar/acabar de trabalhar em breve.

As everyone else agreed it's "(em) breve" But maybe you have also been wondering about the expression "daqui a pouco", which has also the meaning of soon. See you in a bit = Até daqui a pouco. / Até breve.

'I see you soon': vejo você em breve

Soon = breve

Breve :)