Old viewers (LL's v1.23.5 and older, Snowglobe v1 but also v2, old v2/3 viewers and actually, all current v3 viewers) will cease functioning properly (they will be unable to "bake" avatar textures and avatars will stay grey) after LL will turn off the legacy baking service on their grid, sometime next year. While the new baking service is anticipated to come into production sometime in February (if all its bugs have been fixed by this time), the old baking service will coexist with it for some time (probably at least a couple of months, perhaps more), meaning even old viewers will keep working for a little while.So the sky doesn't exactly fall in January as some of the notes being passed around would have you believe. Yay! But it does get a little darker because a lot of people are going to be left behind on their favorite viewers that aren't being actively developed any more.
Ultimately, however, all maintained viewers will migrate to the new baking system, and the Cool VL Viewer will be part of them. No worry.
BTW, I would like to thank Henri for all his hard work on the Cool VL Viewer. It's so much faster than Phoenix or Firestorm for me it's not even close. Henri also seems to know more about what Linden Lab is doing than Linden Lab. :P
The question for a lot of people is what this means for viewers that support other grids like OpenSim? As far as Henri is concerned, he plans to maintain both baking methods in Cool VL Viewer to support other grids. Who knows what other devs will do?