If you think about it, there are very few milestones that have already been introduced and where Baam might wish to stop by either during his climb or once he becomes a Ranker: 2F (been there, done that), 43F (already there), 1° wherever Enne is sealed off, 2° wherever Enryu is located, 3°wherever FUG HQ / Lustec is located, Wolhaiksong on 77F, Karaka's fortress on 97F, 5° Arie Hon's extra test on 100F, 6° : Repellista's castle on 123F, and Zahard's castle on 134F (?). If I'm not mistaken, this covers locations that must make an appearance at some point, though it doesn't mean SIU cannot add ad-hoc locations (e.g., 20F, wherever Workshop Battle took place, Hell Train, Name Hunt station, etc.).
7° : Seeing these, you can notice that there is a potential to skip almost 60 Floor after the 43F, because--even if Baam visits Wolhaiksong during his climb--it's possible if not preferable to include this in the timeskip in the same way as Baam's FUG training. In other words, it's possible that once Part 2 is finished, Part 3 resumes either when Baam is approaching some of the location that are on unknown Floors, or once he's approaching 100F--I really doubt Baam would visit Karaka as soon as he reaches 97F.
That said, the main factor is whether SIU plans to have the story ultimately culminate at the end of Baam's climb (i.e., there is going to be no "after Baam becomes Ranker story"), or whether SIU plans to have Baam complete his climb within the Zahard Empire and then sort out the remainder of the plot. 8° : If it's the former, then the timeskips between Parts are going to be relatively short, because it's unlikely that there would be such a huge Floor gap with no interesting content. However, if it's the latter, then the upcoming timeskips can be really huge, because Baam can revisit the skipped locations when the time is ripe.
1° : Why would he want to go where Enne is sealed ? She's supposed to be a freakin monster that'd be able to kill both him and his friends. She's one of the strongest woman (and one of the strongest) in the Tower. I know that Baam is a really nice boy, but I do not think Garam will ask him to free her or anything. Garam came to her to ask her questions about the Princesses, but they are not close at all, and so, I don't see Baam going to free her on his own, nor anyone asking him to do it. If one would be crazy enough to free her, it would be Mazino, cause he wouldn't have much to fear, as strong as he is.
2° : That, contrary to your previous location, could be an interesting quest for Baam. He might receive a hint on Enryu's location, maybe while going into the Hall of Souls on the FoD, where all the Souls are stored (cause I think the FoD arc will end there with White's ressurection and a big brawl between everyone, but that's another matter). Moreover, Enryu and Baam seem linked to each other (Baam being the God of the Outside incarnated in flesh, and Enryu one of his messengers, if not his only). They also look alike. So, a short arc on chasing Enryu would be possible...
3° : Maybe when he'll deal with FUG himself. It would be possible, since in this arc, HJS could play an important role, SIU even said that he would be more developed later. In a FUG arc, maybe.
4° : Those 2, I am not sure. Baam will certainly meet Mazino again on this arc epilogue, so they won't need to make him go to the 77th floor. As for Karaka, he can't wait for Baam going strong enough to invade his castle or he'll be dead for sure. Karaka knows it too well, after HJS came to see him there.
5° : That's just a test, not an entire arc, or a goal in itself for Baam. Moreover, no one in the 10F knows who he is, and in the Jahad Empire, only the craziest and most paranoid members of it (Jahad's enforcement division) were aware of his existence. If they just sent Ren, it means that they don't really care...
6° : Not sure about Repelista, but Baam will certainly reach Jahad's castle.
7° : That would be quite big... That would also mean that Part 3 and 4 would be focused on 30 floors (100 - 134).
8° : Well, yeah, from here on, you can just speculate, but I don't think that there will be more after Baam become Ranker, because my opinion on ToG's end is that Jahad's system will be destroyed, and the word "Ranker" won't mean anything. But Baam VS Jahad will be the last thing we'll see of ToG, IMO. A battle that'll shake the Heavens themselves, while the 10F will be wrecked out by FUG and Mazino will lead an exodus out of the Tower.
But we have to integrate 2 arcs into this near-future : those were confirmed by SIU in his blog posts (well confirmed I don't know, but he spoke of them = Jahad's Princesses Arc and Khun Family Arc)