The aiming on a controller is good enough with auto-aim turned on and controlling your movement speed is much nicer with analog control. Getting around and in and out of menus is painful with K&M and I'm a bit disappointed they didn't change any of that stuff to be more suitable for a desktop environment. Aiming is obviously much nicer with a mouse but the trade offs just aren't worth it, unfortunately.
IIRC they've put out statements before saying that they agree that their support is lacking and in need of overhaul but that it'll take some time for them to plug the bigger holes. So they're working on it, basically.
Even though I didn't play L4D1/2 very much, a next-gen L4D3 for Xbox One/Playstation 4 would be pretty cool. Although, at this point, I'm scared to even ask for games anymore with exclusivity rights being swept up by both sides. LET ME CHOOSE DAMMIT.
Valve are pretty big on putting their games on as many platforms as they can so I don't think you'll have to worry about that any time soon.