Fairly shocking statement, seeing as it's coming from you - the acclaimed videogame historian.
Are you seriously saying that we should just let some corporation to take care of everything and it will surely make every single game available forever? It's as if various console e-shops never closed down without giving a damn about content, no game ever disappeared without trace from Apple/Google (even Steam I think) stores. As if Netflix model hasn't already proven it's all up to some executive's whim. As if common sense wouldn't tell you that it's simply impossible.
I'm sorry, but that "pluses and minuses to everything" way of arguing just does not cut it. Some little pluses do not balance gigantic minuses.
I'm merely stating that one of the roadblocks to games being available to play forever is the lack of compatible hardware to play them on, which makes them lose market value. Streaming eliminates that particular roadblock, just like for other media. In terms of preservation, I understand that will present some challenges, but the only thing I've seen really thwart preservation efforts is the lack of an available copy of something or a copy that someone else is willing to share, e.g., APL/S on the Videobrain. Otherwise, the data will still be available in some form to potentially preserve. Even in the heyday of physical media, preservation has never been a given. Tons of media has been lost forever.