Do nothing has to be paired with a commitment by the community to not adopt any protocol changes (hardforks) that could result from a Tron witness super-majority. If the community is steadfast in its support of the existing protocol, I think we would win the battle for the true Steem resulting from a fork.
Tron witnesses can do a bad job at being witnesses under the current protocol and the network will suffer to some extent. For example, when they don't update the price feed. But as long as economic nodes refuse to switch protocols, the damage they can do is limited.
That completely depends on how much stake Tron holds, under the current rules. My understanding is that Tron presently holds nominal stake to exercise Steem governance at it's sole option.
Do you have information that may affect that understanding?