Dawn of War was a great RTS game and it has over 6.500 votes. Since GOG has other WH40K games, is there any chance GOG will get this one in the future?

Sadly, at this point we can assume that it's unlikely, due to Sega's negative attitude towards DRM-free (Sega is currently "owner" DoW franchise) and lack of interest in publishing literally anything on GOG.

We can only have hope that something behind the scenes is happening. But I wouldn't raise hopes too high.

As already said above, but in addition to that i believe theyre still honouring free steam keys for those with boxed copies, which suggests the idea of a non-steamworks version is not in their field of view.

Are they Polish-phobic or something?

Its something that bugs me in Japanese media in general... not a single mention of Poland. Usually Russia this or Russia that, but never the Land Between Germany & Russia.

they are anti-pc as a rule

Sega considers drm-free as a xenos heresy, so no hope !

There is ALWAYS a chance. After Diablo + Hellfire and Blade Runner releases everything is possible, literally. Yes, SEGA is the owner of Dawn of War series, and yet Games Workshop is the whole owner of Warhammer franchise. We don't really know what is happening here. My best guess is that GOG client base is still very small compared to Steam (sales figures), so for that reason only they might not be interested to make any amendments in their agreements. Something tells me that we still have to wait for 5-6 more years or so. They have their games available on Steam, so not entirely true.

There are 2 games published by SEGA here on GOG:
https://www.gog.com/games?devpub=sega&page=1&sort=popularity