Steemit is always stays Steemit, but I think everything is depending on the people. It is not a requirement/necessity to write long blog posts on Steemit.
You say "DApps that show only the contents/posts posted via their platform, then microblogging will start to gain momentum. Kinda like how DTube only shows you videos posted via their platform or how SteepShot only shows you photography posts that were posted on their platform or how you can only see questions/answers here on Musing. All of which can be viewed on Steemit. XD"
Well, not all of them. You can't read Musing questions and answers on Steemit.
You can only see "RE: Musing Posts", "View this question on Musing.io" or "View this answer on Musing.io" on Steemit.
Musing questions and answers can only be read on Musing at the moment.