What are the chances this also happens for GTA4?
pretty slim. as Rockstar Games hasnt issue any official respond about GFWL.
Bandai Namco said back in June that they were "seeking alternatives for the game"
Never say never. Rockstar is currently doing some significant updates to San Andreas, and GTAIV has generated a large amount of revenue for them over the years. They may be motivated to keep that gravy train going indefinitely.
Uhm, just a little question about it.
What about people who were fine with GFWL but are not fine with steam?
While those people do exist, they are almost negligible compared to the consumer base.