Yup... positive ;)

Copied directly from HT6.5 announcement (Announcement can be read in full on the Hattrix site):

Skills decayCoaches will now slowly have their leadership skills decay.
Decay will not start until the coach has been in the club for more than a
season. We think it is both unfair to new teams and quite unrealistic that once
you have bought a super coach, you could keep him forever - until he is 100
years old or more. Of course, we could have added an upper limit when coaches
suddenly retire, but we really think it is more fair that they slowly decay,
just like players do, and leave the final choice to you when it is time to bring
in some fresh blood. Our "in character" reasoning is that a coach that might
seem bustling with energy and inspiration when he first arrived, after a few
seasons loses some of his "edge". He has simply grown bored with the job... ;)
Finally, once a coach reaches disastrous leadership (and that would typically
take perhaps 10 seasons for a coach starting with solid leadership), the decay
starts hitting hs trainer skills instead of the depleted leadership. Let us
underline that the decay is very slow, although it will go somewhat faster for
coaches with very high leadership, so a solid leader might go down to passable
after 1-2 seasons (more likely after 2 seasons or more though).