It's more an issue of pride than an actual problem.
There are plenty of guild with 43-47 members and new guilds are opening every day. I every 10th guild of similar capacity (there are hundreds even of 200m+ guilds) broke up (possibly within an alliance, if the problem is staying together with friends), the problem would be solved, but as long as everyone insists on keeping their guild there won't be a solution.
Unless your guild has a strong enough status to attract a surplus of new candidates, of course.