Other games will certainly follow suit so as to avoid the legal repercussions as to the legitimacy of gambling involving digital money comes into question.
EVE Online, the outer space combat game from CCP, has revised its End User License Agreement to prohibit third party trading of items, and most particularly, gambling.
While EVE does not use steam services to collaborate with items, it seems that they are eying to avoid an enigma before it begins, specifically as the game shifts to a free to play system. The legal connotations of allowing a game to become a cradle of gambling are still being debated even today, with administrative boards like the Washington State Gambling Commission launching probes and threatening developers with server distraints.
"The third party service IWANTISK has been shut down in game," CCP states in the accompanying blog post, "and all ISK and assets have been confiscated after extensive and exhaustive investigation has brought forward compelling evidence of large-scale Real Money Trading. Permanent account suspensions have been issued against those involved".
Meanwhile, "the third party service EVE Online Casino has been shut down in game, and all ISK and assets have been confiscated after multiple and sustained breaches of our Developer License Agreement. Permanent account suspensions have been issued against those involved".
"Please note: Given that the Alliance Tournament is currently ongoing, we are aware that some players may have outstanding wagers on alliances who are competing with other third party services who have not been subject to account action and/or ISK and asset confiscation. These third party services are free to finalize these wagers over the course of the weekend given that they have not broken our rules, but must wind down operations in an orderly fashion before 11:00 UTC on Tuesday November 8th, 2016."
You can the full, updated license agreement here.