will L4D2 go any lower?

Unlikely, it's a pretty good deal as it is.

no.all of the valve games so far have fixed discount even if they go on daily.(eg. cs:go z been 50% the whole time)

The game was once free to get permanently for 1 day :)

I think 80% is the lowest it will go for this summer sale.

Don't think so..

You'll never find it for cheaper than it was Christmas 2013, heh.
But seriously though, according to Enhanced Steam, the current pricing is the lowest price in history.

thx for reply guys