How do you plan on altering the app upon the new forum software?
Don't know when that would be ( does anyone really? ) but I make apps with TDD ( test-driven development ). I will be using the current html as test cases for parsing. If/when new forum software appears the job is straightforward ( although non-trivial ) to make the parsing engine handle the HTML ( replace the old HTML in the testcases with new HTML and make all the tests pass ).
Fair enough. Sounds great.
As a recommendation, maybe within v4 or v3, would be to include notifications upon reply to thread if the thread is watched within the app.
Basically the same thing as email notifications, but within the app itself.
This would take more continuous querying to the server however, so it should be able to be turned off on mobile (in case the person is low on bandwidth/data).