The lockdown will be still successful even if inter-state travel is allowed, because people working from home and avoiding contact will reduce the spread. What you can't do is go back to normal until there's a vaccination or antiviral available.
So, you expect some amount of lockdown to continue for years, and perhaps indefinitely? All the "vaccine is just around the corner" claims ignore that vaccines have always taken years to reach the market, and effective vaccines for rapidly changing virii have generally defeated the vaccine industry. Any plan based on a vaccine appearing is not really a plan at all. Its wishful thinking. A real plan has to work without a vaccine, with the appearance of a vaccine being a nice bonus that makes life easier.
What is the alternative? These countries (UK and US) have screwed up and failed to contain the virus. It is wild in the community. If we say ~70,000 deaths due to CV19 (40k reported, 30k other) in the UK, but only 7% of the general population has had the virus, then to let it rip through the rest of the UK would mean we expect around 1 million deaths in the UK alone. That is worse than Spanish Flu. (228,000 dead in UK estimated.)
1 million deaths in the UK, at the end of the epidemic, would only happen if something goes horribly wrong, such as a massive runaway infection causing the hospitals to choke up. 70k excess deaths so far already sounds pessimistic, it's probably more like 60k, but 65k is what was reported a week ago, so let's assume that's correct for now.
https://www.eveningexpress.co.uk/news/uk/excess-deaths-in-uk-pass-65000-what-the-latest-covid-19-figures-tell-us/If we assume the Office for National Statistics antibody testing report giving an infection rate of 6.8% of the population, then we can say we've roughly had 4.6million cases so far, leading to an average excess death rate of 1.4% per case, weather this be direct or indirect.
As of 24 May 2020, 6.78% (95% confidence interval: 5.21% to 8.64%) of individuals from whom blood samples were taken tested positive for antibodies to the coronavirus (COVID-19). This is based on blood test results from 885 individuals since the start of the study on 26 April 2020.
https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/coronaviruscovid19infectionsurveypilot/12june2020Fortunately, it's highly unlikely the entire population will become infected, because as more people develop immunity, the R number will gradually fall, until it drops below 1, since even those who haven't being exposed to it will be surrounded by those who are immune and will never get infected. This is why it's so important to prioritise the most vulnerable groups of people: older, male, and of black and minority ethnicity. It's generally accepted 70% of the population will need to have been exposed to gain herd immunity, so assuming that's right, 70% of 68 million is 47.6 million and the excess death rate is 1.4% per case, giving a total of
2/
3 million excess deaths.
I think if we're successful in containing the outbreak, the total will be around around double the number of deaths is expected. This new drug will help to reduce the case fatality rate and hospital capacity won't be exceeded, so they're shouldn't be any more deaths due to cancellations or fear of going to hospital and getting COVID-19.