Tom Service of the Guardian has an excellent, and surprisingly candid, interview with the Boston Symphony's Managing Director Mark Volpe. According to this profile, the problems that led to Levine's departure were as much about the BSO playing 'second fiddle' (no pun intended) to the Met.
Service seems to think that the BSO will opt for youth in its next director. I disagree with him. As frustrating as James Levine has been for them, I don't think they're apt to quickly forget what might happen if they get stuck with a young dud as a music director. After thirty years under Seiji Ozawa, the thought of another uninspired director leading them for a generation probably induces horror. I very much hope that they will not go the way of the Chicago Symphony/Philadelphia Orchestra/every ageing orchestral dinosaur and hire an interim 'principal conductor' who is too old to beat time. There is no better way to let standards slip than to have a figurehead who is only in town for 6 weeks of the year. But my guess is that they will opt for an older director, like the New York Philharmonic did when they hired Lorin Maazel, who can complete the job of restoring the luster of the BSO which Levine began. Whomever that is, they will use him as a stopgap to search out for a younger and more ideal match who can stay with the Boston Symphony for the long-term (hopefully more than twenty years). Riccardo Chailly still has his Leipzig commitments but there is already talk of him coming over in 2012 for an 'audition concert'. If the orchestra approves of him, there should be no doubt the entertainment in the headlines will be equal to anything in the concert hall. Perhaps Semyon Bychkov is a more likely candidate as he currently has no permanent appointment, but I can't imagine the Bychkov train being any less turbulent. If they want a drama-free stopgap, they need a boy scout like Zombie-Carlo Maria Giulini. Ironically, Christoph Eschenbach, who spent years salivating after every Big Five Orchestra he could position himself for, might have been ideal for this type of match. My own personal opinion is that they should hire a dull-seeming American like David Robertson who could grow into the role and whose musical curiosity will make the orchestra think differently about the way they play music.
In any event, we will probably get a far better sense of exactly who's in the running when the BSO's schedule for next year gets released.