You do not need a negative test to enter France if you are fully vaccinated with an EMA approved vaccine + 7 days.
You do need a negative test to return, available in pharmacies, though the are now charged for tourists and you should book in advance (in person on arrival seems fine currently).
However things are changing literally on the fly and this text maybe out of date by the time it has been written.
The go is, if you want to travel to France the French are ready and willing to accept you, only if you are fully vaccinated, and the Government seem very keen on making this the goal post. Entry to bars, restaurants and hotels is restricted unless you have a health pass showing a negative test within 24 hours or are fully vaccinated, this is for everyone, including staff (who can have 1 jab done, and must have the second done by the end of August). These measures are in place to avoid another lockdown and give the tourist season a chance.
Extremely harsh penalties apply if you do not follow the rues as a business, €45k fine and up to 1 year in jail dependent on the severity of the infraction.
So in answer to your question, I think France will be open until at least the end of August, they are trying everything to make this happen. Will they red list Brits? Complete guess but the quarantine on return will restrict movement anyway, so as long as this is in place on the UK end, the French policy should remain in place. If it is lifted it may shift.