Since the sharedrop is 1:1 with no shares brought into existence, then it does not follow to me that BItShares stake holders will be hurt. BitShares might be hurt or might be helped, but it seems likely that shareholders would benefit.
Forks didn't kill Bitcoin. They spawned a legion of developers.
Bitshares will definitely hurt. Some developers move to the new chain which will slow down development. Some investors will sell their BTS to buy shares from new chain, which will lower the price. We might very well get all time low, if other traders realize that developers are leaving Bitshares for a new project. Some active users will leave our internal exchange, which decreases trading. Some members of our current community will stop marketing Bitshares and focus on the new chain.
BTS-owners will get new shares in sharedrop, but it seems to me that tonyk have no idea what he is doing. Quick and half-assed fork will probably fail and the value of new shares will remain very low, so it doesn't compensate the losses from BTS price decline.
We are not in the same position as Bitcoin was. There is no surplus of developers eagerly waiting to join a development team. Talent has been already scattered in hundreds of different projects and it's quite difficult for new projects to attract people who know what they are doing. It might happen but I wouldn't count on it, especially if the project is founded quickly and haphazardly.
If there is going to be fork, it has to be done properly. The goal should be the destruction of Bitshares so that there won't be two competing projects that will eat each others resources.