We’re at a point in franchising history where three films will no longer do. Series from Die Hard to Indiana Jones have been expanded beyond their trilogy borders to include a fourth entry; meanwhile, the future third film in the Hunger Games saga is already being split into two parts. Traditionally, conventional wisdom marks the third film in a trilogy as the lesser installment of the series, but as three-parters get expanded to four, so too is that adage stretched out– and if The Bourne Legacy has anything to add to the discussion, then the fourth film is the new third. Call it tepid, call it slack, call it pointless;…