In fact there are many more overlapping/redundant extensions. Consider for example the real estate TLDs:
.property .properties .realty .apartments .homes .condos .villas .mortgage .rent .rentals .house
plus the variants in foreign languages
.pics .pictures .picture
.photo .photos .photography
And maybe more in the future.
Yes, this is confusing. I ...
TL;DR No one can predict the future (so theoretically the case you present can happen, in practice I wouldn't bet on it), especially because ICANN, in charge of TLDs creation has a lot of rules and procedures, that change over time, with decisions that can later be appealed, reversed, upheld, and redone. So expect the unexpected.
Now, in more details (the ...
No, it doesn't mean .coms etc will become available at all.
When the gTLDs were expanded, companies applied for the new extensions and for whatever reason they were granted by ICANN.
It is pretty unlikely that they would ever add an s to the well established domains.
If you have a look at Patrick's answer to this question - Will .day TLD be available to the ...