Senior people leaving after a big acquisition isn't a sign of things being screwed up, but rather the normal run of events. There are many reasons, but the main one is that people who were already bored of their work are now given a strong reason to retire in the form of a sizeable financial payout. That payout is in exchange for the standard "no leaving for X months" contracts that key contributors have to sign during takeover negotiations.
But to answer the question: Qt was acquired from Nokia by Finnish IT consultancy Digia which then renamed itself as The Qt Company. The platform is still active in the embedded device and in-vehicle product segments.
I don't actively use Qt anymore, nor do I have any connection to Qt - but if you're considering a cross-platform toolkit for devices, you could do worse than visiting www.qt.io