The short answer is, "When European gas storage units are full".
I came across a very interesting table on gas storage - here is a screenshot:
As you can see only Poland, Portugal and the United Kingdom have their gas storage facilities over 90% full.
Everyone else is still scrambling to fill theirs. Most have caved to Putin's demand that Russian gas be paid for in rubles. The fear is that when winter comes, Russia will turn off the gas to put pressure on the Europeans to stop helping Ukraine. Having full gas storage units acts as a cushion against that, hence the frantic buying.
But as long as everyone is frantically buying, it's a sellers market. Only when the storage units are full will the prices come down. Spot prices in the UK have already dropped, to the relief of the electricity companies who use gas to generate electricity when the wind farms are still.
I think Russia is trying to prevent them filling their storage by reducing what it sends through the pipelines.
So the prices should start to drop by the end of summer?
Yes. Especially if we have a late summer and mild winter.