Ever since Elon Musk took control of Twitter, there has been a lot of personnel issues with a large amount of senior management and senior developers either being fired or quitting. This has lead people to question whether T will go under. This in turn has lead to some providers to start to look at other social media platforms with IG being one of those landing spots. Tumblr is another I have heard about. There are also a number of other platforms that are not that large at the moment, such as Mastodon.
All that said, it is unknown if T will collapse. If there is a collapse, it won't be quick. Reports indicate any collapse won't happen until the beginning of next year at the earliest (now watch it shutter next week.....)
If it does start to shut down, here is link to an article about how to download your tweets.
https://www.washingtonpost.com/technology/2022/11/18/download-tweets-twitter-shut-down/
It has always a good plan for SP/MAs to have a backup (IG?) in case they are banned from T, which happens from time to time. If there is a collapse, those who have a backup will be alright. Those who do not will have some catching up.
So at this point, I would just keep in touch with your fav SP/MAs and ask if they have a second social media account somewhere else and join/follow them on the second platform. I'm not going to give up on T just yet. EM dropped some big time coin for T and I don't don't think he wants to bankrupt himself.