Based on what metric? Media stories, and YouTube fanboys aren't a metric of the level of,fan interest. The media said the same about Star Wars a Solo Story, female Ghost Busters, Star Trek Discovery, Star wars the last Jedi, and yet sales of merchandise and fan interest is down, and how is this the first time seeing a female lead? There's been tons of them since the mid 80s. This is the first female Doctor, but as far as female leads, I would hardly say modern Who is all about one character. If you really think about it, Rose, Clara, Martha, and Donna had a ton of exposure. I would go so far as to say modern Doctor Who was as much a co-star scenario, as aposed to single actor focused. Also, this new direction seems to be a return to ensemble casting. So we'll see. But I'm interested to know HOW you can say There's a majority of fan interest..when there aren't any numbers or metrics that can give an accurate view of fan interest. Like I say, it all comes down to the viewing figures, mid season. Those curious would fall off by the middle if not interested. The fact a female is the lead, is a shallow argument and akin to only taking an interest based on her Gender, which is what everyone was defending as NOT the focus of her casting, that she simply was the best., and oh..wait.,yea, that was later disproved and shown to be a lie, that Chibnall picked her because he wanted a female all along.,so really, when it comes to news about Doctor Who, and all the explanations, touting, hype and such. I tend to take it all,with a grain of salt. Proof of success will be in the viewing figures. Either Doctor who is on the rise to its glory days. Given the rework of everything from logo, to set, characters, monsters, filming and episode count, to include debut day and time. Or this will not get above Capaldi's ratings, and if below, then that is the fandom the BBC is left with after Moffat's tenure, and trying to grow from there is tough. Especially if the traditional fans have had it with the series long before Chibnall and Whittaker were announced. Most of my Friends left after Season 7 and never looked back. I stuck in until season 9..then I was forcing myself to watch until I am up to date. At which point. I could see why it's ratings suffered.
Bottom line, if we want to gauge excitement for the fan interest in Jodie Whittaker and Chibnall's 13th Doctor, then it will come in with mid season ratings. The initial bump from debut could also be telling. The debut has to be around tenant numbers to be a complete success. But if they can't achieve that level of interest, and the ratings are at, or around Capaldi's era..then a decline soon follows..then the show is not gonna be as successful and so many try to hype, with no basis in fact to back that up. Except personal enthusiasm.
Character Options toy sales, Titan books sales, and merchandise will also be tell tell signs of the new series success. Will the classic stuff be a bigger seller? Will the new series merchandise be bigger sellers? Or is there a sales bump overall or a decline overall between classic and NuWho. That would indicate interest in the brand all together has waned. I don't want to see that, I prefer the series continue. But those will be the numbers that will tell ultimately how well this new iteration of Doctor Who does, and if it's sustainable for the future.