My feeling is Bellucci wil be Blofeld for the next film.
The current Blofeld is just a decoy. Witness how in Rome the SPECTRE guards knows Bond is coming. Only Bellucci would have tipped them.
She would be amazing as the bad guy for the next 4 four films.
Or alternatively - SPECTRE has just lost a senior member, Lucia's husband. The board would be one down. Assuming everyone bar Marco Sciarra turned up (they wouldn't dare otherwise, I think!) the guards would be puzzled to see an unexpected "member" turn up - complete with entrance pass, Sciarra's ring. Notice how after Bond has got past the bald goon, the one of the other two reaches for his mobile? To ask if this man is expected?
(Admittedly, only to be told "No, but let him in anyway. Our leader has a pretty good idea who he is!" ;-) )