Will they be added in the near future? Or is it pointless to wait?

Update: Answer to user Patias from developer Tyrone Rodriguez:

There’s a technical limitation that we’re trying to work with GOG on

i hope they add it

That's exactly what I want to know.

This situation is becoming annoyingly frequent lately. Hope GOG to do something regarding this.

In the meantime I'm not buying this awesome game

To be honest, a "external" achievements isn't most importantly for me. This is just addon only.
The most important thing is that game has not DRM and it is supported on a par with other platforms(updates, DLC, bugfixes, etc).
That why I waited for TBoI so for long.

If I did not have my own internet connection, then achievements would be nothing to use for me.