The concern I see being expressed, fundamentally, is "I have developed skills, practices, and efficiencies with current Wiki syntax. Is your new parser going to destroy my investments in learning? am I going to have to start over with this new system?"
As I understand it, for the foreseeable future there will be a raw wiki syntax interface available. I hope contributors can be reassured on this point.
We are trying to provide an additional, easy way to edit the WikiText of regular content pages. This should not interfere with diffs or otherwise mess up existing WikiText. See many previous posts in this list for technical detail on how we are trying to ensure this.
If WikiText was to be ever removed then there would need to be a very good way to handle all of templates, parser functions and so on. Visual programming does not seem to be as popular as some people expected it to be in the 80s, so I won't hold my breath for markup to disappear any time soon.
Gabriel