I wouldn't write a publisher acquisition for Sony off the table just yet. Between PlayStation Productions, PlayStation Plus, and PC ports, Sony has a lot of ways to leverage content libraries from midsized publishers like Square, Capcom, Ubisoft, etc. The unlikely options are massive publishers like Take Two, EA, Bandai Namco. Sony have said they are willing to allocate more funds if necessary, but the question will remain if the acquisition is worth it.
At the very least, I hope Sony isn't taking consolidation lightly, otherwise they could be in for a rude awakening by the end of this decade. All it takes is Microsoft wanting to acquire another publisher like Ubisoft and slowly choke Sony out by removing third party content from PlayStation platforms.