so C.I. survived and with 3.0 it saved me from Lara-Hell ?

Many applications still run CodeIgniter 2.x fine.

If you build something with CI3, is it really a big deal if CI4 comes out and you can't switch it over? I'm sure CI3 will run applications for years to come.

If you insist on using the latest version at all times though, then you may just need to spend some time migrating to CI4 when it's out - if it does break things.

Worst case scenario though: it just takes some time to upgrade it. Keep your code clean and decoupled and it shouldn't be too bad