Yes, so far seems like there isn't very much to change so it will be more of an update. The biggest change possible is callback concept but most likely it has more drawbacks than benefits so that we'll improve includes.
Auth system is quite painful. On one hand, we want it to be more detailed and have control over every option and every group (some people even request control over every user). From security point of view, ACL alone is not enough and is combined with hierarchical model. But even as it is now, auth system is huge data and slow access. I'm afraid before we add more and more items, we need to find some smart ways to make auth system more compact and faster access.
Finally I've completed my "callbacks vs. includes" experiment and here is the summary:
- XCache is good for your health. With XCache there is absolutely no difference between callbacks and includes, not to mention things go significantly faster.
- Without XCache includes are 5% slower than callbacks in loops and both are almost the same in normal hooks.
- It takes 2 minuts to convert 1 plugin part to a callback.
To conclude it, callbacks are not so great on performance as we supposed. If 5% is really important for you, then your site is popular enough to run a dedi/VPS or at least ask your hoster for XCache.
So we will focus on improving includes() and architecture changes won't be so dramatic.