Well might be in SL 3.5 as KDE 4 is not yet stable. Could be by sept / nov 2007.
It is one thing to have a piece of hardware not working or partially working but KDE + bugs is a good resepy for disaster unless you use Gnome aarrgghh. Whole new can of worms you are opening this way.
Also for testing you would have to run a stable copy of linux / SL and then use say virtualbox / vmware with SL + beta KDE , as getting it wrong leaves you with only a format + reinstall if you do not know what is happening, this makes it easier with updating the linux copy , local repository folder can be reused / shared = less download and main SL install on hd is safe (host) . Could even have a stable install on virtualbox and zip / rar or similar and if major stuff up happens tehn delete virtual hd and unzip from safe backup = 30 min.s instead of install + update + customize = 5 hours later.
You would also have to have stable linux + beta kde to make sure you have actual kde bugs to report and not distro bugs affecting kde beta , this might end up being a bit tricky to achieve.
I was going to try KDE 3.9 the other day just did not get to it yet.
SL development or KDE development:
Problem if not yet stable enough to use / test = most new users / old user would have to spend time fixing KDE 4 instead of spending time on SL except for aaarrrgghh Gnome user they can get on with their lives.
No problem to help them out at KDE but 15 milj possible users and about 10k for SL = SL needs more help at this stage and redhat / all the other linux distro's is already helping KDE so if they can not get it working between 15milj users / contributors then extra 2k - 10k will not even make a dent.
Remember this pay's for some / most of SL developers food / rent etc . So getting it wrong means hungry devlp. and slow down in SL as they would have to get other sources of income , might be the end of SL or at least a huge delay time wise.