The Coalition for a New Dallas will probably continue on without him. Did the coalition support tearing down any other Dallas freeways besides Interstate 345?
The Coalition was against the Trinity Toll Road. Of course they succeeded in getting that project killed, largely by getting anti-tollway council representatives elected to Dallas City County. That was not a simple task to accomplish, and showed that they had political savvy, influence and clout. But killing the Trinity Toll Road was relatively easy, since it had marginal support and was so expensive that no one (including NTTA) wanted to build it.
IIRC, the Coalition published a proposal to redo downtown Dallas freeways, which of course included removal of IH 345 and also relocated Interstate 30 well south of downtown, placing it along the two railroad corridors (on a much longer route). That plan was somewhat ridiculous, which was good in my opinion because they lost a lot of credibility. TxDOT is now preparing to move forward with rebuilding IH 30 in its current location.
So I think the only item still in play is IH 345. As you mention, the Coalition for a New Dallas will probably continue on without him. But will D magazine still be its mouthpiece? And will it still be as active as it was in the Wick Allison era? That remains to be seen. But I think there's a good chance it will be less influential without a leader as committed as Allison.