In this YouTube video min 0:32, Dr. Samir Gupta, says
It typically would last for 12 to 18 months
In How the Pandemic Will End in the ll. The Endgame section:
No matter which strategy is faster, Berkley and others estimate that it will take 12 to 18 months to develop a proven vaccine, and then longer still to make it, ship it, and inject it into people’s arms.
Why?
Under the assumption that infected people become permanently immune and stop transmitting the disease, the virus will eventually just run out of people to infect. Currently the "R" value, which measures the average number of people that an infected person contaminates, is somewhere around 2.5 if people behave normally. R below 1 means there will be less and less infections until there are no more infected.
In this graph of the spread in Germany from February to early May (source) you can observe R > 1 in the left half and R < 1 in the right half:
There are 3 ways this can happen:
A: If a significant percentage of the population catches the disease and becomes immune, the R factor will drop (if you are infected and half the people you would have infected are immune, you will infect half as many people as you otherwise would have infected, thus R is now cut in half). In some countries this approach is practiced against chickenpox.
B: Vaccination can provide herd immunity just like A, but requires a safe vaccine without side effects, that must be manufactured in massive quantities. It's estimated that the development of such a vaccine will take 12-18 months, but this time frame isn't guaranteed.
C: Temporary changes to society (contact tracing, quarantines, social distancing, masks), or the environment (heat, humidity) can significantly modify the R factor. If the changes push the R factor below 1 and are sustained until the virus is gone, this will end the pandemic. This is what stopped SARS.
In countries that practice C to some extent, A is not going to happen this year. Because there is no consensus among countries to eradicate the virus by means of C, C isn't going to happen in the foreseeable future. Which leaves B as the most probable outcome at this time. And B is widely reported in the news media to be ready in 12-18 months time.
Things will change when there are significant changes to the projected timeline for B.
The last flu pandemic (Spanish Flu), lasted from January 1918 until December 1920. If my human calculator is correct that is three years. So 1 to 1.5 years seems almost optimistic.
Top US health official says the coronavirus is 10 times ‘more lethal’ than the seasonal flu would be 500 million assuming Spanish Flu was 50 million and Novel Coronavirus is 10 times worse. On the other hand maybe the Spanish Flu was just like the Coronavirus, we simply do not know. That said the experts "guesstimate" of 12 to 18 months might be too pessimistic like you hope or too optimistic compared to the Spanish Flu.
The good news is if every nation could be like China and attempt to catch every single case the virus will end.
The bad news is more than 10% of infections in Alberta (where I live) are healthcare workers who spread it at home and when they go shopping. In the old days they lived in hospital residence. In efforts to make things better we are unwittingly making them worse.
China on the other hand took seven idled cruise ships and moored them for healthcare workers to live in comfort. It's not just Alberta that has healthcare transmission, 13.6% of Spain's infected are healthcare professionals and 51 doctors have died in Italy.
The moral of the story is if you stop the spread you stop the virus. If you don't stop the spread you accelerate the virus.
Finally consider the current strategy is to slow the spread, not to test for the spread. (I can provide sources if desired). This means it could lengthen the disease duration until herd immunity, unless a miracle wipes it out.
April 3, 2020 Update
Today Ontario said the Pandemic would last 2 years but praised themselves for reducing 5,000 deaths to 1,600 deaths for the month of April.. But of course it was all fiction because it was based on "what ifs".
Personally I hope we can wrap things up with an action plan in 30 days but barring no plan I suspect 3 years and not 2 years like Ontario forecasts or 1 to 1.5 years like OP forecasts.
Sadly it appears no one is in charge.
