From my own experience, this is your employer doing something unethical and dishonest. There are laws in the USA that protect "whistle blowers" from backlash, but you'll have to research that in your own location. Also, this only protects a person if they go to the authorities, rather than the public.
If you company really is closing and going to be leaving your customers "high and dry" without products they paid for and with no way to get a refund for the products and services paid for but not delivered, this is not legal in most places and highly unethical.
Since you mention this might be a ploy to get rid of people near retirement, there's plenty of doubt on the closure of the company, too. However, trying to push out people near retirement before paying for the retirement earned is also highly unethical and a shady business practice, in general.
I'd start looking for a new job, regardless, and try to have one lined up before you quit and/or are laid off due to closure.
Since there's doubt about the company closing, I'd keep quiet for now, or you're guaranteeing trouble and possibly the closure of the business. If it gets down to less than a month and the business is showing obvious signs of shutting down without telling customers, you might want to go to the authorities to let them know what's going on.
Years ago, I worked for a company that sold computer components to businesses, not only individual parts but also some bulk sales. At one point, headquarters told the manager that our store was staying open for 2 more weeks, then closing the doors and we weren't supposed to tell our customers. We were supposed to take orders and make sales as usual, which the HQ wouldn't actually honor since they couldn't get the parts anyway. My boss told me to keep quiet and that he would tell the customers the situation, which he did. He did that so I wouldn't get in trouble, but also so that the customers had correct expectations.
It's entirely up to you if you tell the customers, but I'd definitely research the protections as well as the consequences in your jurisdiction before you do anything. Fortunately, it sounds like you have time. Well, as long as no one else leaks the info. Good luck!
I've removed sections that talk about tell the customers and either replaced those sections or added other wording to suggest going to the authorities instead. Of course, this all depends on the laws of the local and higher governments a person has to deal with. Always do your own research before acting on the law or against a business. Businesses can have rights and protections similar to people.