1. gradually, more vendor lockin (read: not plain markdown) features are added
2. greater focus on monetization
3. exit
4. go to #2.
In some products this doesn't matter. In a personal knowledgebase it might.
The only thing you could get locked out of is the convenient curation that Obsidian provides
Im normally opensource-or-bust but the way obsidian is set up is pretty low risk
Having watched this movie a few times, I like to have the insurance policy of open source licensing so that it stays true tomorrow.
Once something is proprietary it's arguably easier from a developer perspective - and preferred from an investor perspective - to make it steadily more proprietary over time.
Then one day you wake up and even if your notes still aren't saved in some some obtuse format that only loads properly in Obsidian, your experience has gradually degraded but by this stage you've got so much tied up in the proprietary extras that you stick around unhappily.
I feel like it's quite a well-worn page of the tech playbook and I'm probably only scratching the surface here.
And the second they go full evil, I can just point _any_ editor to the same directory structure and stuff will mostly Just Work.
I also want open-source for PKM software but I realized I value getting things done more if there were no near alternatives for my use case. I tried Logseq but it's straying even further from vanilla Markdown than Obsidian and is not as well-polished.