[saghm]

If he had gotten the citizen by now without having had to renounce his British citizenship, would he be forced to renounce it if/when Brexit finally happens?

[dukoid]

Dual citizenship is discouraged but I don't think officials would care enough to actually "force" anybody... https://www.dw.com/cda/en/dual-citizenship-granted-to-most-n...

[detaro]

From what I've heard it seems like no, the double status is likely to be allowed to continue.