I think that sometime near the end of the next book; because the book is supposed to take place over the year following Murphy's death and LTW promised Harry he'd get back to him after one year, LTW comes back and tells Harry he can't give the him full answer; because Council politics or the rest of the Senior Council are afraid of Harry, or maybe some of both, but LTW can share some important; though probably obscure, tidbit of information with Harry. Maybe it will be about the history of the last major Starborn who was involved with Winter and the Council, or maybe it will be about the Stars and Stones or perhaps it will be a cryptic clue such as, "When the (Fill in the blank) happens, the answer you are searching for will (more fill in the blank). I don't think it will matter very much what LTW tells Harry, with the possible exception of the cryptic clue which would at least give the readers something to look out for.
What could be more interesting is where Harry goes to get the rest of the information he believes he needs to learn. I'm not saying Harry will get this information from Bonea, but he's certainly going to be tempted to do so. My guess is the first source of information will try to tap is Bob, but Bob's information will be somewhere between limited and nonexistent.
To get to the OP, I don't think Mac will give Harry everything he needs. However; like LTW, Mac might give Harry a valuable clue, but probably only if he's asked in the right way. I think Harry might have to tell Mac that the Council is afraid to tell him what it means to be Starborn and this has made Harry worry that he might not be ready. This kind of honest self doubt might persuade Mac to give Harry the help he needs, though probably not a complete answer in and of itself. Mac is far too terse in his use of language to give Harry the Starborn user's manual. Plus, in Mac's own words, "I'm out." So that leads me back to Mac not wanting to openly take sides, but deciding to share a vital clue with Harry.