If you base that argument on say the Spanish flu epidemic, then without a vaccine back then, it would have been prevalent for years and years and years (it stopped after a second wave). The whole point of a virus is to survive - by infecting. If it can’t survive, it mutates - and the mutation is more likely to be less virulent than the the original virus, to allow it to survive. So it may become part of every day life for us, just like flu and the common cold. But that doesn’t mean it’s going to kill us all and life stops. Who knows exactly how many people may have built up some immunity in the U.K. too, which may be contributing to the daily decline that we’re seeing, despite lockdown being lifted and mass protests that we have seen for many weeks. We just don’t know that number/% of the population, given so many people being asymptomatic. That could be a huge contributor as to whether we see the virus return in bigger numbers again. A second/third wave may well happen, who knows - but it’s not guaranteed.