I don't think that the central Steem team will withdraw delegations once SMTs are launched.
One of the main differentiators between Steem dApps and the companies they are trying to disrupt is the potential to earn rewards. Take away those rewards and the Steem dApps lose that key element which raises them above the competition.
I would expect the Steem team will want to continue to support the dApp developers and their independent additions to Steem infrastructure. These help make Steem the most active blockchain with one of the strongest communities.
My guess is that the Steem team will be targeting established external companies for SMT adoption. These companies may buy into Steem to support their SMTs by a mix of SMT and Steem rewards.
But more importantly these companies could attract a new wave of Steem users who could buy Steem as a gateway to buying SMTs - in a similar manner to Etheruem and ERC20s. The battle will then be to convince these companies to keep their Steem once they have sold their SMTs for Steem.
That gives a more likely pattern for the existing dApps. I do agree that if the current dApps have very successful ICOs then the central team could withdraw the delegation. However this would only be likely once the dApp had built up their own Steem (and then SP) through the ICO sale. So this would be more a way to prevent large sales of Steem following a successful ICO.
At the same time the central team will not want to discourage SMT adoption by dApps which could be the case if they withdraw their own funding after the ICO. So a careful process of communication will be needed to make sure everyone is working in the same direction!