Bill will be on Tuesday night (along with Bob Dylan, should be awesome) but the final show is Wednesday night. So Bill won't be the final guest unless Dave just doesn't have any guests on Wednesday night.
I'm not sure if Wednesday's show will have guests or not, but you'd think it would. Bill being the last guest was discussed when Howard Stern was on last week. During the interview, Howard began speculating on who the last guest would be. When he mentioned Bill, the logical chose, Dave's reaction was that of a person agreeing, though he didn't announce anything definite. Big secret , I guess. Not sure why this was the case, struck me as odd when I was watching it, but Dave's reaction seemed to let the cat of the bag. We'll see.
Been really interesting to watch the show the last month or so, as all of the show's best guest have made an appearance. Some of the guests have been overcome with emotion saying goodbye to Dave. Which isn't really all that interesting on it's own, but when you try to understand the reason behind their emotion, and how that relates to the pit in your stomach, things start to get interesting.
Norm McDonald's appearance the other night is an perfect example of the personal connection some have to the show. Norm's reaction was so out of character, Dave was taken aback by it.