Following Aurilian's withdrawal, the Free Dacians reconquer the province and reconsititute a Dacian Kingdom. Roman emperors would campaign against them for nearly fifty years after this, including Constantine the Great who took the title Dacicus Maximus in 336.
Following this and under Constantine's influence, the Dacians convert to Christianity and the bible is translated into Dacian. This helps cement the Dacian identity and they are among the missionaries to the Germanic tribes. If they ride out the Hun and Avar invasions, they may be able to assimilate the incoming Slavic tribes (although Dacian would absorb a lot of Slavic loanwords)