I think Sony sent a strong message with the annoucement.
Towards PlayStation 4 owners and intenders, not MicroSoft.
They made clear there won't be a successor available in 2019, and they also made it very clear that investing in (digital) games & services within their ecosystem will still make a lot of sense in the upcoming 1,5 years since you'll be able to use them on your potential next-gen console right away.
Making sure that whatever MS announces in June will be matched from a technical level (especially with regard to the SSD) is just a bonus.
That said, I believe people drastically overestimating the impact of the next console's hardware since - at the end of the day - both consoles will probably be quiet similar from a tech perspective.
So both Sony and MS will have to focus on services (like cloud gaming, game pass, etc.) and add-ons like PSVR to differentiate themselves from each other AND the current gen 4K consoles they already sell.
I'm pretty sure Sony is "concerned", giving how important PlayStation is for them. But definitely not because of "hardware". That's the very, very least of their concerns.