I personally don't see a need for it, there are many wonderfull platforms for the .45 ACP, and many upcoming platforms for the .45 GAP. The BHP's best selling point, is that it's one of only 2 (that I can think of) pistols that fall into the category of well built, SA, Hi-Cap 9mm. the only other I can think of is a CZ75.
17+1 rounds in a SA semi auto that feels like silk in my hand is why I've wanted a BHP for a long time, and I why I finally settled for a good quality clone (FEG PJK-9HP) when I couldn't afford what I wanted.
So as to the question of .45 GAP, I answer, "WHY?"