But why is this an issue? The source code is available under GPL and LGPL regardless what the company does. If they would decide to no longer open source their fixes or new releases the community has still the source of the last release and can continue to maintain and develop it. There are several large open source projects which are driven by a large community; so even if the Qt Company would no longer maintain Qt (today about 50% of the commits seem to come from the community already) then others would I'm sure.

Currently I mostly see an issue in the fact that an open source developer contributing to the Qt repository run by the Qt Company signs (by action of checkin) a contributor agreement which lets the Qt company use the contributions of the developer commercially and file a law suite based on code provided by the open source developer. If there was a Qt fork independently managed by the Qt Company (e.g. on Github) people could contribute without this issue.