That is likely only if 10% of the boys are disappearing. This sometimes happens such as in wars (a big problem in Europe in the 20th century) – but not likely in our community. It could be many boys will decide to be “gay” (common among secular Jews, not among our community). It could be that boys are more likely than girls to go “off the derekh” – no evidence of that. It could be that Baalei Teuvah and Geirim are more likely to be female than male – but again, no evidence of that.
It could that both genders are “spoiled” and will likely postpone marriage until they have the economic means to support themselves in the style to which they were accustomed – so marriage age will increase. If that occurs there will be less pressure on our schools since there will be more parnassah and fewer children – but there is no sign of that happening (when in happens you’ll notice schools closing for lack of students, tuition falling, etc.).
All young people have a “shidduch crisis” which lasts until they get married. That has always been the case. The only one who really had an insoluable problem with Adam ha-Rishon (it require divine intervention to solve his shidduch crisis). Being worried about getting married is part of growing up – like pimples or having physical changes or suddently realizing the grownups think you’re an adult. THere’s really no hiddush here.