We'll see. There's also the possibility of upgrading to three birthdays a month (especially when we've already got three Leos and three Geminis in there). We also never thought they'd actually do two birthdays a month, yet here we are. Besides, some of the Stellars will be quite lonely as it is, such as Libra and Capricorn (the latter of which never got a proper birthday episode thanks largely to Monica being made for free and getting her first birthday AFTER the first anniversary), so it's actually better if they do three birthdays a month. Not to mention since DOAXVV's pretty much DOA's lifeline at this point, they're probably going to need to do more than three girls at this point especially when adding girls in is pretty much the only thing keeping the game alive outside of collaborations, and heck, they even added an option in the third anniversary leadup survey for wanting more girls from the main series. Even Sakuta D. never necessarily ruled out them appearing altogether, so it's best to be patient (and believe me, I've waited 15 years for Misty to come back, I'm probably capable of holding out for the long run if I must, and I'm not even that patient of a man normally).
Heck, speaking from experience with MGSV when leaked details didn't reveal the full extent of what they were adding in and I was left with my pants down when they added even more than before regarding weapons/base colors and even weapons designs, they're probably going to add more girl slots in. We're already past the girl slots that Doge uncovered anyways.
On the topic of Lobelia, though: Her fourth episode from what I heard did unveil some key details about herself and Fiona. Specifically, they're childhood friends, and they lived in the same area, which means she most likely hails from the same country Fiona does (which, if her Christmas tree fairy reference is of any indication is most likely the United Kingdom).
EDIT: Just remembered something else, we don't even know what they're going to do with the bouquet suits, especially when the two flowers we've gotten thus far via Nyotengu and Kokoro don't even match up with birthflowers. For all we know, Monica and Helena (not to mention any other girls that share a birth month) may end up getting completely different bouquets. At least with Stellar and Jewel, we could predict what the other girls would get based on Tropical Zodiacs and Birth Stones, while we really don't have that for the Bouquet. So we really can't say for sure they'll stop releasing girls, let alone not add the cut girls, after December, November, and April are taken care of. I might as well also point out that Sakuta D. also indicated in the interview that he intends to get the girl release stuff back on schedule to being three per month and has absolutely no intentions of slowing down (Patty and possibly Tsukushi were outliers due to COVID-19). And don't think for a second they won't do three birthdays a month. These are the same guys who pushed five collaborations in this year alone, one of which was completely unannounced, and also was a huge drain on most people's wallets. I think they can do three birthdays a month or even four birthdays a month if they thought they could get away with it.