When will GOG version of skyrim get the creation kit? I tried to ask GOG support but I got no answer.

Not even sure if we'll get it. Gog is working on trying to get it though.

https://www.gog.com/forum/general/release_the_elder_scrolls_v_skyrim_79ad7/post80

If GOG support doesn't know and/or won't tell you, then there is no possible way that we customers can tell you any real & accurate answer.

Although I wouldn't assume that GOG will get it eventually. Maybe GOG never will.

It's possible it might come sometime, but it's equally as possible that it won't ever come.