Witcher 2 featured in the Summer sale again?

It may appear in community deals or flash deal again, if it doesnt there's always Steamtrades.

Unlikely. But you can expect it to be heavily discounted often this year, while CD Project is pushing Witcher 3.

It'll almost certainly show back up. Steam always recycles some of the earlier deals later on in the week, and typically the last two days are entirely recycled deals.

Sure, usually every daily deal are also available on flash sale and community choice sale. And it was one of the best seller of the first day, so we can expect, maybe, to see it featured in the Encore day sale.

Almost certainly, it's likely to show up as a flash sale or community pick at some point, though it may not be the exact same discount.