I agree that doesn't put all money into Bitcoin, because it's much volatile and anything could happen at any time. However, even on beta software, I am still not worried.
Honestly, I'd really like to know some opinions on what the risks might be if bitcoin was beta software, have you thought about it?
I think it'll stay until there's no more significant changes to the code like has been said above. It might remain in beta for a long time more and I don't think that's a problem. Sometimes companies release beta updates a week or two before the main stable update and make them reversible - we might not yet know if we need this with a future bitcoin fork.
One of the main things I can see aside from forks is mining. What if someone somewhere produces really powerful mining chips and has a monopoly on it by being able to mine at a low rate (this might be on the extreme as it'll probably not take too long for companies to catch up and compete but it might pose a risk still too).
I think it's kept with bitcoin core also because it's a flage that might welcome feedback and people to join the team to fix bugs and submit reports maybe that one bug that doesn't do much now could do a lot once a feature it effects gets implemented differently.
A lot of companies also come out of beta to charge people to use their software too - like Microsoft did with windows 10.