The suggestion tracker, it seems to me, is an asset to the development team. Their time is limited and valuable. Why ask them to follow various suggestion discussions when we can help them by writing up a thoughtful suggestion?
As for the community and our opportunity to bat around ideas, we've had area51
for years, since before 2.0.0 release. My thought is that adding a forum for discussing ideas would be redundant.
So really, in my view, we already have the best of both worlds: something concise for the developers, and something less structured for community interaction over ideas, even over features already in a development version.