With Game Stadia from Google launching this year,i think it will have a tough time atleast at the starting for 2 simple Reasons:
Always Online and No Offline Play
As it is a streaming service,you always need to be online.
Also,it is available on multiple platforms with different processing power and different architectures so games won't be playable off-line even if they wanted.
An Alternative is PlayStation Now which is playable online with streaming but certain games are also playable offline as the processing power is available on PS4.
The only solution to this would be standardization of Gaming Processing Power and Architecture like we have for Video.For example a Video is playable on any platform as long it is of a certain codec and Resolution.
For example a 4K MP4 video is playable on Modern Computers or TVs or Phones as it is standardized and it is cheap enough to emulate on most platforms.
For gaming an processing power is first of all not standardized and keeps improving.We need to get to level which is good enough.For example Intel Mainstream CPU processing power hasn't changed much for the last 5 years.
Software standardization can be done with software Tools and Emulation.
But there is also that Processing Power needed for gaming is expensive and not like processing power needed for Video which is pretty cheap.
I think we will reach atleast some standardization of hardware in 10years time like Apple Shifting from Intel CPU's to ARM Chips on Mac Computers to standardization between Computers and Mobile Devices and that ARM Chips will have Good Enough processing power in 10 years to challenge Desktop CPU's needed for Gaming.
Also ARM Chips are cheap so we will in future see TV's,Tablets,Phones,Computers so all will have the same architecture come at a low price.
In future we will be able to download games on any TVs,Computers,Phones,Tablets and play offline like we now download and play video or songs
Games Library & Exclusives
It will have difficulty getting a good game library at first and with PlayStation Now and upcoming xCloud service which already will have a good game library,it will have a tough time competing.
It will also have a tough and long time before exclusives come to the platform.