If colleges allow deferred admission, as long as the entrant notifies them by the required date, the college cannot change the rules midstream, saying, "Yes, we said you could take a gap year, but too many people took this option, and now we're telling you that you cannot, even though you informed us by the deadline - and BTW, you might have to pay 55K to sit at home and take your classes online for some or all of this year." I don't think that parents and students would take that, paying so much for an online, at home experience. If my child were a senior, I'd definitely tell them to take the gap year option, and make alternate plans for this coming year.
What might an accepted student do for a gap year this year? There is a worldwide health emergency going on that largely does not affect healthy 18 year olds who don't have risk factors. Every single aspect of healthcare institutions, nursing homes, our food supply chain, education (assuming that the schools are able to open at all), the funeral industry, practically ANY job that puts people in contact with one another that is considered essential, ALL of these jobs will need workers who are at low risk, so that workers at high risk can remain isolated. So rather than a gap year going to an exotic locale to polish up their high school foreign language, how about a gap year working the bottom rung in any healthcare related field that requires no or minimal training, or the bottom rung in the legal aid office? The possibilities are endless. And the time they spend doing that work might spark an interest that turns into their career focus.
But this still doesn't change the fact that this year's high school juniors are likely to be facing the most competitive admission year there ever was, because of the expected huge number of deferrals. So, does it make sense for them to plan for a gap year (hopefully by then the traditional options will have opened up, including international travel), and wait to apply until the summer right after they are graduated from high school?