I really don't think it's necessary to add more weight classes.
Weight is just one size property. There's also height and reach. And even having more weight, or even just more muscle, isn't purely advantageous, as it also reduces speed. Weight classes are there just to make fighters face fighters of a generally similar size. The idea is to prevent HUGE weight differences that would occur if there were no weight classes. Generally, fighters are of a similar weight as it is.
That's the athletic side. There's also the branding side. Every weight class is a brand, with every weight class comes a new title, and titles are worth money. However, as more weight classes and champions are added, each individual weight class and champion is devalued. Dana White himself has made this point before, citing it as a problem within boxing. I think we're already at that point. 8 male divisions and 2 female divisions (potentially 5 with 105,125,145) is enough. A good general indicator of this fact is that by adding more divisions, we'd start diluting even the NAMING of the divisions, ie. 195 = Super Middleweight and 175 = Light Middleweight. That might sound like a minor thing, but it does matter since we're talking about branding, as it makes it harder for fans to even remember divisional names and distinguish between them. I've already spoken to fans who don't know whether certain top ten fighters are FTW or BW, or BW or FLW, for example.
On the mens side of things, 115 would obviously be the next division to add at the lighter weights. I think the reason UFC would go for this would be to try and gain footing in markets like Mexico and Asia where fighters are generally smaller. But I don't think they'll add the division until they start seeing more quality fighters fill up the 125 division (it's still one of the least populated divisions in the UFC), OR the champion starts actually making money for the company. Higher up in weight, splitting 170 into 165 and 175 would be the next logical step, as 155 and 170 are highly populated divisions. A 195 weight class would probably follow. I don't want to see either of these things happen for the reasons explained above. Then, even higher up in weight would be a 220 or 225 Cruiserweight division, and/or removing the 265lb Heavyweight limit entirely. They absolutely shouldn't do this until the LHW and HW divisions aren't terrible. There aren't enough talented fighters who weigh that much. For that to happen, the UFC would have to start being more competitive with football and basketball to recruit the bigger athletes.
On the womens side, I can see them adding 105, 125, and 145 divisions once the current divisions have established themselves more. I don't think they'll do it any time soon because they need to allow the 115 and 135 divisions to fill out. If they added 125 then they'd replace having 2 thin divisions with having 3 thinner divisions, and still have only 1 female star.
