As per the Daily Mail, Chelsea and Besiktas have agreed a fee in order to allow Demba Ba to depart. The paper is reporting that the agreed fee is about £8 million, down slightly from the £10 million Chelsea were initially asking.
"Demba Ba is an excellent player. We have been in talks with Chelsea for a long time over bringing him to Istanbul."
"Talks are ongoing. Chelsea initially wanted £10 million for Ba but we have negotiated a price we are happy with. We'll tell the media once the final deal is done."
-Fikret Orman, Besiktas president; source: Mail
At the price being mentioned, Chelsea would show a decent profit in this season's FFP books. They'd also save a good amount in wages, as Ba's proven track record in the Premier League led to the player being awarded a fairly substantial wage when he joined the club a year and a half ago.
If the report proves accurate and Ba does leave, that would leave just Diego Costa, Romelu Lukaku, and Fernando Torres as realistic options. There's also the off chance that Patrick Bamford could have a role with the Chelsea first team, though given his limited experience in the lower levels of English football, I'd think that's unlikely at best.