If I build on the Minecraft beta, will it save when the Update comes out?

So, your worlds aren't actually gone... they're just saved on the beta build of the game since you had loaded them up and saved those worlds in that beta. The only way to get those back on the public version of the game is by waiting until the public version
of the build that was in beta (that your world is saved on) comes out. Normally, it just displays it as being grayed out on the worlds list... it is kind of odd that they've just straight up disappeared but I would assume this still holds true. Unless you
had the save backed up in the first place, the only thing you can do is wait until that build comes out.

I'd shoot a message to Mojang's support about it though: https://help.minecraft.net/hc/en-us

I'll also drop this here for future reference: https://help.minecraft.net/hc/en-us/articles/360040841471-How-to-Join-and-leave-a-Minecraft-Beta

Hey there! So the beta version available through the Xbox Insiders Program is very liable to crash. The best thing to do if you are running and experiencing stability issues (something that is lined up in the FAQ about that version in the XIP app) would
be to fill out a ticket/feedback/report in the app or directly on Minecraft's website. When you load up the game and see that world pay close attention to the file size, in my experience with that in-progress-build of Minecraft world saves over or around 150
to 200 mbs (megabytes) tend to crash. Naturally the problem will ride itself out whenever the game updates or there is an update to the build being ran. Don't try and de-enroll that world/game version out of the beta as any worlds running beta content (for
example yours since you moved it up) wouldn't be playable until the next update. I would just keep trying and send in a support ticket where appropriate.

Have you both checked your system for updates to make sure you are on the most current build of Minecraft? I know when I was using the Beta version of Minecraft I wouldn't even get invites from friends but as soon as I left the beta and installed the normal
version I was able to receive invites and accept them.

It's a glitch with the player save data on the map.

playxbla.com/check-out-whats-coming-in-the-update-for-minecraft-xbox-360-edition

Lol. I have been around for a while and when a beta sucks the fanbois always say it is an old build. They say it will be different on launch. lol. Wake up yougsters. What you see is what your going to get. There will be no new build that blows you away.
if your not happy with the beta then your not going to be happy when it comes out.