The (one?) female he was bred to is gravid. She's already said she is going to keep all the offspring and watch for signs of the same thing happening. I can't imagine Rosey would ever sell a snake that she thought there might be a chance of it developing cancer later in life due to a genetic defect, especially after losing her own in such a way. Leonardo was an amazing animal and what would you have her do? Throw out a clutch of eggs produced by an amazing, favored snake just because there's a chance the offspring might have the same issue? If they do, then none of those offspring will be bred and that will be the end of that. If not, then she's got babies of a snake that was lost due to cancer and while it won't be able to ever make up the difference, at least she may have a baby she can look at and go 'yeah, that's him'.