In LinuxQuestions forum, there is an ultimate mega thread called "When Will The Next Slackware Release Arrive" which discuss when will the next Slackware will come out and other things, such as what is the default kernel which will be used in the next Slackware release (up to now, Patrick Volkerding always put kernel 2.4.x as the default kernel in Slackware), what udev will be used, and many more. It has been made sticky also by the moderator, since many people have asked the same thing on the Slackware category, so they combine all of those post into one big mega thread. When i post about this, there has been 12 pages on it with 175 replies.
Waiting for the next Slackware is really interesting, since Slackware is basically a one-man project (Patrick Volkerding), so he takes charge of the Slackware development by himself (even though he generously takes advice from the community about the packages, like Piter Punk). This way, it's up to him to decide which packages should be the default and which one should not be included in the next release, including the kernel selection. Even though many people have urged that Slackware should come with 2.6.x kernel (and it's also mentioned several times in the Slackware-current changelog), there is still some consideration about dumping the 2.4.x kernel since it's still used by many many users around the world (mostly because it's stable enough). At the other side, those kernel wasn't updated regularly, since Linus is prioritizing on 2.6.x kernel and the 2.4.x kernel didn't support more driver than ever, so people tends to use 2.6.x kernel since it's more stable, supports many hardware, and it's faster (in some cases). If Slackware comes with 2.6.x kernel, i think it will be 22.214.171.124 which was the last stable kernel in 2.6.16.x tree. The reason why Pat don't use 2.6.17.x kernel is that because this kernel has introduced so many changes and it will take some time to test it (which is not good for production level to use untested kernel as it impact the stability of the the system). Maybe the 2.6.17.x kernel will be introduced in -current after the Slackware 11.0 has been released. That way, he can start breaking again (also testing and fixing) in -current :D
For me myself, it's not a problem what kernel version will be used for the next Slackware, as i always build my own kernel by compiling it from source. But i will need the Slackware ISO as a new base when i want to install a new Slackware. Up to now, i have been following -current development, so i don't have to do a clean install again, since i have the latest packages in Slackware (which eventually will be released as Slackware 11.0), BUT, if something goes wrong with my system and i have to do a clean installation, i will need a good base and that will be Slackware 11. If i use Slackware 10.2, then i will need to do a lot of updates (that's equal to 9 months of development cycle in Slackware). If i have a Slackware 11.0 CDs, then i will only need to do clean installation and update the latest packages counted from Slackware 11.0 release date.