Lols, but no, Britney will be below Beyonce once Beyonce's career is finished.
Britney was done and stamped by 30. Beyonce has continued into her 30's with multi-platinum albums, all-time grossing tours, highlight acclaim, GRAMMYs, and peak starpower.
Only so much longer the Army can keep holding onto "she did this in 2001 tho!" to combat 2015+ receipts.
Longevity will always be the winner.