I think the very least they can do is make the necessary moves to ensure that certain key franchises to their brand don't end up belonging to their rivals. I do feel like they need to put aside any reservations they have about getting a publisher with the rate things are going with MS though, otherwise they're potentially stuck competing against an absolutely massive first party stable with their current studios and likely wouldn't be able to contend with the sheer volume of major franchise games such a large rival would pump out.
Sony have at least 10 billion left in their budget for acquisitions as of last year and were hiring for positions that specialize in mergers. Hopefully they plan on doing something outside of scooping up unproven live service devs.
Part of these $10B, which were not only for acquisitions but also for investments, and not only for gaming but for the whole corporation, was already spent to buy:
-One of the biggest actors of live service games in consoles, the one who set the record of best selling new IP in gaming history popularizing live service games in console. They also created Halo before that.
-The developer of a live service game for mobile that generates to Sony over a Billion dollars per year
-A new veteran studio with key people behind record breaking AAA new IPs like Assassin's Creed or Watchdogs, and also many other top selling blockbuster AAA like Rainbow Six Siege, other key live service game in the consoles and PC market, which is also one of the top games in eSports
-A new veteran mobile gaming studio with key people from top live service games from mobile, consoles and PC such as Supercell, King, Rovio, Digital Chocolate, Kabam, Wooga, IGG (all of them top 5 worldwide in mobile gaming and/or browser gaming live service games in different ages of history, just in case you don't know them), Rockstar or Wargaming
-Investments in gaming and non-gaming companies, such as Epic (unproven makers of the live service game Fortnite or Unreal Engine), Devolver (Fall Guys and others) and From Soft
-Non gaming acquisitions
Yeah, much unproven teams and much unproven business model. It only generates the majority of the gaming revenue worldwide, same as mobile. And like mobile is also the biggest growing business model of the market since several years ago both in users and revenue. So I wonder why they would want to invest more on it.
PlayStation's division posts several record numbers every year and grows in many areas and is the market leader in consoles while MS lays off 10000 people and after spending almost $100B still can't compete against Sony in gaming. MS is the one who has to take decisions to become competitive, not Sony.
Now seriously: yes, even considering all this Sony still has budget, acquired people related to acquisitions and will continue acquiring. But pretty likely won't buy big publishers at least soon.