They will eventually fail altogether and the bike will just stop. If this has been going on for a while, it's doubtful that adjusting the slack will fix it either. When the clutch is adjusted so that tension remains in the cable, the plates gradually start slipping a little under high loads until they are worn so bad that the owner finally notices the problem, and by then it's too late. High speed slippage will wear the plates rapidly.
2004 Rebel 250, 2003 BMW K1200GT (roadburner), 2004 BMW R1200GS(all purpose),
1973 Norton Interstate (in a box in the basement)
1968 Triumph Bonneville