i would doubt that support for markdown would be removed, but how it gets interpreted could change. for example, support for tables are technically handled only as extensions of markdown, and there are different variations of extended markdown. so some markdown interpreters might handle |-|-| to define a table, but others might require |---|---|. that said, the interpreters that handle |-|-| will also handle |---|---|. so as long as you used the latter (more universal) syntax, i don’t see any reason why that would ever break in the future.
iNat already uses different interpreters for the web vs the different mobile apps, and there could be minor differences in the syntax that they handle. so you may want to check that your markdown works (and looks reasonable) in both web and app, if your potential readers could use either.
more info here: https://forum.inaturalist.org/t/help-needed-to-make-the-new-markdown-code-for-table-work/14728/34