@Mario Andhika it's probably a relatively safe time to use Kobweb. We don't foresee too many more deprecations before 1.0 (and recently things we do deprecate are often esoteric features). Hopefully soon we will start focusing 100% of filling remaining API gaps and missing widgets, and then we should be 1.0. (In other words, the framework isn't going to really change at this point -- just the feature set will grow).
Of course, it would be worth knowing what other technologies you are considering, and if you have any hard constraints / goals with the site you are planning on building.