Right now, pretty much any structural move by the company is going to further the notion of a potential acquisition, but the Metro article is a bit misleading.
SEGA SAMMY Holdings (the main parent company) merged the remaining two SEGA businesses into a single company, SEGA Corp., and dissolved any shared administrative functionality between the SEGA business and their other company, Sammy Corp. Even under the new structure, the SEGA business still has responsibility for creating arcade & certain amusement machines, while Sammy remains focused on pachinko, pachislot, etc. and their related operations.
As for Nagoshi, his title is now Creative Director. In all likelihood, with the combined SEGA company, it probably no longer made sense for him to sit on the board of directors, which is now all business executives and not creatives. For clarity, the company currently recognizes three boards: the parent company, SEGA, and Sammy. Nagoshi always sat on one of the SEGA boards and was not a director of the main, listed parent company.