Well the list of suspects has already been created and as you said anything at this moment is just guessing, The hints that Gosho has given are very vague and all that we could do at this moment is to create a list of suspects though I believe there isn't much clues to go with. We could eliminate who is NOT the boss.
For example, Shuichi Akai can be removed from the suspects list because the Boss called him at some point the "Silver bullet". The same goes with Vermouth who is said to be the HIS favorite agent. We can also remove from the suspects list professor Agasa, because it would contradict half of the storyline as he was protecting Sherry and Shinichi. Kogoro and Ran Mouri also don't fit on the suspects list, for one thing the Boss ordered the assassination on Kogoro and Ran for obvious reasons.
At this point as I said we can only make a list of suspects and a list of who's absolutely NOT the Boss of BO. But we will have to wait for more clues from Gosho. Anything regarding the Boss at this moment is very vague.