Don't think Carrot will join the strawhats for the same reason i didn't think anyone else would join the strawhats: Because it's been almost 400 chapters since Brook first appeared. And i'm sure if Oda intended for anyone else to join, they would have joined then.
Doubt BB just wrecked Dragon. Revolutionaries are too big a part of the story to just get offpaneled. They could easily have escaped, or even curbstomped Blackbeard with lots of collateral damage.
I agree with that logic up to a certain degree. There are indeed many people who seem to be underestimating the importance of the time-skip and think that anyone can join at any time, which is really not the case. The time-skip was almost a point of no return as you can't just keep adding Strawhats simply because if it's too late in the story, that character's development would be redundant, forced or non-existent. Before the TS the Strawhats just did everything on the spur of the moment. The TS was the first and only time they ever seriously prepared for something and this for a period of two years. This creates a bond between the Strawhats that would be alien to any other future Strawhat. Hence why I also always have been skeptical about new Strawhats.
However it remains a fact that Oda himself set the door open somewhere in the SBS or in an interview in regards to new Strawhats and that Luffy said all the way at the beginning that he wanted 10 crew members and so far he only has 9. There's also a reasonable estimation that currently the story is around 2/3, which means there's still 1/3 to go and I believe that's still enough time for at least one member. Of course that member should be joining about now, so Carrot appeared on the ideal moment.
From all the characters people have been suggesting as the newest Strawhat, Carrot by far has currently the highest chance of actually joining:
1) She's female
Considering the current ratio is 8 males for 2 females, female characters have a higher chance than male characters to keep things more balanced.
2) She's a mink
Luffy has a love for the weird and the unusal. A cyborg, a human reindeer, a skeleton...so a female rabbit surely would be a perfect match for the crew.
3) Personality quirks
Almost all Strawhats also have weird personalities or some weird quirks. A chronic lier, several perverts, a gold digger...now this is rather common for many characters, not just the Strawhats, but still Carrot has showed to be rather odd.
4) Strength
All the Strawhats had to train for two years, which makes it rather difficult for anyone to join as that person needs to have a certain amount of strength, however it would be rather illogical that all the Strawhats had to train for 2 years, but that someone else can join just like that and keep up. So there has to be something that balances out that 2 years of training. Now Minks are born warriors, they have a natural aptitude for fighting and Pedro implied in this chapter that Carrot's strength seems to even be for a mink rather high.
5) Adventurous
IMO this might even be the most important characteristic of Carrot. It was quite strongly emphasized this chapter that she has never left Zou and is severely naive in regards to the outside world and as a result she's highly excited to the prospect of traveling around. This is a quality many other characters that people have suggested lack and it's a quality many people also seem to ignore. For example characters like Rebecca or Viola had no reason to leave and this also applies to Vivi. She is the sole heir of a mighty country and her father is in bad health, so she really can't just leave to go on an adventure.
The only thing so far that Carrot is lacking, is a position within the crew. All the others have a defined position: navigator, shipwright, cook, doctor etc., but what is Carrot supposed to be?
