An Air Herald publication reports that “jailbreakers according to the hacking team Evad3rs they should stay away from iOS 7.1.” The reasons are not known, and by clicking here mentions that maybe the group is disbanding.
According to the publication in question, the team does not provide a reason why jailbreakers should not upgrade to iOS 7.1, but it likely has to do with the fact that Apple has closed all known iOS vulnerabilities. Since iOS 7.1.1 replaced iOS 7.1, the same appliesnotice and for the newest firmware.
The publication adds, “… one of the team members mentioned that evad3rs seems to no longer be focusing on iOS 7.1 as a team,” suggesting that they are probably disbanding. Of course, it won't be the first time that a dev-team doesn't agree with all its members about something project.
The infamous Dev-Team, of which the famous is a member hacker pod2g, had broken up and then reunited, adding some new members to replace those who left to become evad3rs. According to his publication Air Herald it seems that this group has done its circle.