Would Bismarck and the twins simply be trapped in Brest?

Would Bismarck, Scharnhorst, and Gneisenau just be pinned in Brest if they survived the sortie?

Probably, with another Channel Dash as a possible escape, but their combined Atlantic threat would still be much greater before they reached port.

German capital ships reaching Brest could be pinned there and might eventually need to repeat something like the Channel Dash. Containment after the sortie, however, did not neutralize what the ships could do while still at sea. Adding Bismarck to Scharnhorst and Gneisenau would greatly increase the force required to protect a convoy. The answer separates the later basing problem from the immediate operational danger of a concentrated raiding group.