As long as they keep themselves in the news cycle they'll be fine tbqh. No conferences last year and a lot of media attention from a non gaming event shows they don't have to be there.
Besides, we don't know what their alternative plans are yet.
Hey, maybe Sony doesn't even need marketing anymore. I mean every other successful business tries to market their products, but Sony is a special company where all of the executive's farts smell like roses. Why does Sony even need marketing when they are launching a big new product? Right? Surely they can afford to skip the biggest gaming event of they year when they are launching a new system? Right?