Per the Premier at the latest press briefing on March 10, the vaccination target for Cayman removing the quarantine for those visitors who have 1) received their last vaccination shot at least two weeks prior to travel, 2) had a negative test result within 72 hours of their travel, and 3) tested negative on arrival is now "70-80% of the total population" being vaccinated - which was later clarified in the briefing as 80%. The Premier also implied that at that point, anyone who wanted to come to Cayman could do so. (Currently you have to be a citizen, resident, property owner, close relative of one of those - or connected).
The exact percent target still seems to be an open issue, as well as what constitutes "the total population." If children are included in total population, then achieving the 80% target will be difficult under any circumstances (We are currently at almost 40% of total population, and at over 90% of over-60s). They did say that they are planning to lower the age of vaccine eligibility from 16 to 12 years old.
(Btw, having hit the 90% target for us old folks, the quarantine period was reduced to 10 days as of yesterday.)
Cayman will have enough vaccine on hand by April 7 to vaccinate every adult in the country, and the premier suggested it would be early May before they could all be administered, assuming everyone was willing to get vaccinated. I know many folks here who are hesitant to get the jab, however.
When asked later by one of the press about some specifics on border opening, the Premier replied that there are "some months" before they would have to resolve the issue.
The other factor to consider is that Cayman is having an election April 14, and the current administration seems more amenable to opening that the opposition. So opening day will probably also depend on which party or coalition ends up controlling the legislative assembly.
And finally, the latest rumor going around with some of our local friends was a June 5 opening. I don't give that much credence.
Sooo.... putting it all together, I would not expect to see the quarantine removed until sometime this summer.