Have they shown the final Steam Controller design yet?

I except it to flop if there are no new games from valve who will be using this new engine which is very likley

It'll flop like Unreal 4 did. 

/s

Anyone worried half life 3 will be exclusive to steam?

Let me guess. Will be a very awesome, successful and acclaimed engine but there will never actually be a Source 3.

Why wouldn't it be exclusive to Steam?

Why is this something worth worrying about?

Half life 2 wasn't 

YES! YES! It's finally happening. Well, I guess it's not quite Half-Life 3 but Valve actually doing something games-related for a change. Also, Steam Link sounds awesome. Streaming games from my PC to TV is something I've been looking into recently and apparently it costs a ton (wireless HDMI is expensive). Might also want to try out the Steam controller, depending on some things.

Do you mean console versions or are you just crazy?

Like WoW,D3,Hearthstone,Starcraft II etc are exclusive to Battle.net/Blizzard client.

Most Ubisoft games to Uplay (even on Steam I start games and they launch Uplay and cnanot run without their client so it's Uplay by default) and then most EA games being on Origin.

I don't see the problem at all seeing as how the other games are sold on Steam and Steam being the biggest store so far with the most users, the series and store are both owned by Valve, it would be like saying people were worried a Sony owned IP was going to be exclusive to their system or service, of course it would and it would make sense.