I agree the most likely scenario is that world will have travel restrictons in place for quite some time.
I am not so sure a vaccine will ONLY take18-24 months though, and it's not obvious (for me atleast) that a vaccine is the ONLY route.
If for instance a drug is found to remedy the effects of the virus enough so that another outbreak won't owerwhelm the health systems, I see no reason why they wouldn't open up sooner.
For instance: 3 days ago a new chinese study on the by now famous malaria medicine hydroxychloroquine's effect on Covid-19 was published. Granted, the study is not peer-reviewed and the sample size was small, but main findings were that 0 of the 31 patients that received HCQ progressed to severe illness as opposed to 4 out of the 31 in the control group. Study can be found
here.
I'm guessing that study is the reason Trump mentioned it again at his presser today as "very promising" (or whatever he said. I'm not suffering through that press conference again to get excact quote)
From my understanding hydroxychloroquine is only one of atleast a couple of dozen already developed drugs that's being tested around the world on their effect on Covid-19, so the drug-treatment route could quite realistically be a faster approach to "fix the problem" than researching a vaccine.
When it comes to the timeline for developing a vaccine. I think Faucci and other have said that the 12-18 months for a vaccine is optimistic at the best of times. For instance: We're almost 40 years into the AIDS epedemic without medical science being able to find a vaccine for the HIV-virus (and it's been heavily researched). On the other hand we've had a medicine to completely surpress it for what? 25 years of something? Not saying Covid-19 and HIV are comparable in any way other than both being viruses of course...
Just my 2 cents, but it gives me hope that the number of people succumbing to this might not get as high as different models predict and not as important of course, but still, that normality of life and international travel might open up a bit sooner than the time it takes to get a vaccine to market.
Disclaimer: I'm not a medical proffesional in any way shape or form.