Will the UK quarantine for arrivals be lifted? I am going to be traveling from San Francisco to London July 5th?

The government is currently advising against all non-essential travel to and  from abroad, and hasn't given a date for when quarantine will end.

It won't have been lifted by the 5th July. Cancel your plans, or prepare to spend 14 days in quarantine on arrival. 

No and I hope you have a guaranteed address to quarantine for for 14 days otherwise if you do not have suitable accommodation to go to,you  will be required to stay in "facilities arranged by the government" at your own expense for the 14 days

Not for some time. 'Quarantine' means you have to stay at the same address for 14 days, not that you are led away and locked up somewhere for a fortnight.

Probably not for US citizens.  In fact, most European countries are about to strengthen restrictions on those traveling from the USA.

Not with the USA yet.

The latest information is on the link.  The government are negotiating "Air bridges" with some European countries at the moment.  The USA is not on that list, so it is likely that you will have to quarantine when you arrive here.
https://www.theguardian.com/travel/2020/jun/26/what-are-bridges-where-do-they-go-will-they-affect-my-holiday

No chance by then.
UK

Not in the near future I'm afraid......there is no sign of quarantine being lifted and will continue while we have a few idiots who continue to ignore the rules.

Not yet.  It's only just been imposed!

No. The US has the highest number of cases of COVID. Other countries don't want us bringing it in. I hope you have been following guidelines- wearing a mask, socially distancing, etc. If not, you can only blame yourself for the continuing travel restrictions. You can go to the UK, but then you MUST isolate yourself for 14 days. People are being arrested for breaking quarantine.