I think we are a long way from dilution. But, yes, it can get crowded. Right now, most of these platforms are experimental. Some will be loyal to Steemit, some will be loyal to Minds, and others will be loyal to Narrative or Trybe. A few will jump between them all. Some, probably a large majority, will remain stuck on legacy platforms, at least for the time being. "Dilution" won't happen until Facebook starts losing users to blockchains. That will be a while yet.