PC ports are generating them hundreds of millions in profits with no negative effect in game sales, which are selling better than ever with a 50% of new users who never had a modern PS console before (or at least did use a new PSN account).
They also achieved last month a record MAU in PS, meaning their userbase is growing. Sequels of games previously ported in PC like Spider-Man 2 or GowR had all-time record sales.
If there is any effect is positive, increasing console hardware and 1st party game sales in console.
I think that if they use their own launcher will be to integrate a portion of their ecosystem: things like trophies, PlayStation Stars, cloud saves, friend lists or maybe even unify it with the already existing remote play and cloud gaming PC apps in a single one.
If this is the case, and specially if they also implement stuff like cross-save and cross-buy between PS and PC (only for this launcher, not with Steam and Epic Store) it will be more likely that some PC users may do the jump and get a PS specially after having built some catalog on PC.
The launcher and PC store may need some time because they need to build first a big enough PC catalog to make it worth for players to move there.
what will be the differenciential for us console players that invest 400/500 on a console to play?
Tons of console only and particularly PS only games. Sony won't port all their games to PC, and excluding some MP focused GaaS, the ones ported to PC are/will be released around two or more years after their original release on PS. So far the range of ported games is 2 to 10 years after their original release.
Plus the plug an play experience, not having to worry about drivers, performance, etc. and also stuff like the PS+ collections, PSVR2 and a better hardware pricing: you can't get a gaming PC of that performance for that price.