[2020] Old saves on 9.0

Hi! I am new one to that subreddit and fairly new to game. So my question is:

- what is going to happen with our saves after 9.0 update?

I did some research prior asking but it is really hard to google "eco" without finding lots of actual ecology related stuff :)

I personally ok with starting new world from scratch but I made a mistake gathering my friends to play session that close to new update and one of my friends, well, he is kinda not like starting things from the scratch after doing some progress...

So if it is possible to continue on old save, how we can do and what it will cost us in terms of gameplay? And if it is not possible - can we at least somehow port to new world our buildings, save some kind of progress?

P.S.There are 3 of us so we are playing 1-3 world with me being host, in case it somehow relevant