Will GK1 20th Anniversary e GK1 be united in the future, like Baldur's Gate, Broken Sword, Icewind Dale?

Doubt it, for a start both games have a different publisher.

I read in another thread on this board that Jane Jensen licensed the rights from Activision to publish the GK1 remake. That means she had to pay Activision money for the right to sell the the GK1 remake game for a limited amount of time, until the license expires.

On that basis, I predict that the GK1 remake will go off the market (meaning no one will be allowed to buy it any more) once the license expires, similar to what happened with the games Mafia 1 and Alan Wake, which were taken off the market because the licenses for their music expired.