They won't fix it completely. They can't. Fixing bugs with spaghetti code is like playing wack-a-mole with a steel mallet. The game itself was built on a shaky foundation and DLC after DLC, some which have deep game changing effects, have made it, well, far shakier I guess. All software has bugs, though. Even had the base game been rock solid and every DLC QA'ed to perfection, there'd still be bugs.
Then again, modders were able to get Sims 3 into a playable condition, so it's likely that some of the fundamental issues with Sims 4 will be adequately bandaided eventually.