When will this becaome a problem?? Not for a long time. Colonization of other planets will be available eventually. People can live in antartica if they have to!
At an inpersonal piont of view, The people with the most risk of passing on heretitary problems to their children should be the first barred from having children. People could maybe adopt a child. There are many children that are waiting to be adopted, and lots never do.
But personally I think that the idea is very wrong and corrupt.