How long will this coronavirus last for? I hope it gets better I will be traveling to UK in July. I hope I would be able to go?

I really hope and pray things will get better but we must prepare for the worst case scenario. The virus is likely to last all year. Some are even saying the grim will continue till the northern summer of 2021, until a vaccine is found, which I think is an exaggeration. But do not worry, the situation in Wuhan is getting better which explains en masse lock down works...The airline is optimistic that they will be able to fly after 31 May, but if they cant they will most surely offer you a refund. 

July NEXT Year.  I would cancel any flights for this year.

It's impossible to say for sure but it will probably go in waves depending on your location. Restrictions will be loosened after the number of new cases in your region shows a steady rate of decline. This could be two or three months. Maybe a little sooner if you're in a region that will hit an apex sooner like New York, or maybe longer if you're in an area that's still in its growth phase by that time. If you look at Wuhan as a model, they hit their peak about 10 weeks ago and are just starting to to lift the lockdown now. However, once restrictions are relaxed there could be new waves of infections, albeit it less severe as some people will be immune. If it reaches another apex that overwhelms healthcare you'll go back into quarantine, and so on in cycles, but each subsequent wave will be less severe. These cycles could continue until there's a vaccine in 12-18 months, until there's a medication that can be reliably scaled and distributed, or until herd immunity kicks in.