Today AltSpace announced via https://altvr.com/important-information-for-altspace-world-builders/ and on their Discord server that there will be further updates required for those who have already updated their worlds and assets to 2020.3*. Unfortunately, anyone who has already updated will need to follow an update process (again) to make their assets compatiable for future updates.
No doubt this curveball in addition to the already stress of having to update existing assets will fuel further frustration in the community. As I had already opened up and created an Excel spreadsheet to keep tracked of everything I have to say it is annoying that I will have to open up all of those projects again.
If you have not yet upgraded to 2020.3 and are still using 2019.4, we recommend that you do not upgrade. Stay on version 2019.4 until we let you know to make the switch. And don’t worry, your worlds will continue to work!
If you haven’t updated yet the official advice is not to bother and wait for further information. I 100% back this advice personally as well.
An official date for….getting a future date for the upgrade
AltSpace has committed to having a future announcement by the 16th of July which from the news article suggests there will be tools released to support the development further.