Eh, hold your horses!
On one hand i'm pretty sure there will be no wipe for skills, ever.
On the other hand, there's many not so obvious ways to "adjust" the balance between avatars, and avatars Vs. mobs.
Skills can be nerfed partially - by introducing new skills in the future that we don't have today or creating environments/activities/items that use our existing skills differently (eg PvP environment where your HK only heals at 25% efficiency)
Skills can be nerfed indirectly - by releasing new weapons and creating new mobs with higher damage (that also require higher avoidance levels). If at the same time skilling speed is also increased considerably the overall effect is actually a nerf of existing skills.
etc etcActually, the devs have warned us all these years that adjustments like that are possible in the future. Life goes on and things change, that's only normal. If i was the most skilled avatar in game, i can't expect to still have this position after being away from the game for years. However, if u serious hardcore player and u stay with the game - i'm sure there's no need to worry.