No Hawaiian Airlines will maintain its own brand in terms of service.
All the current Hawaiian menus will be valid until February 2026, so I don't expect big changes until then.
They are changing to AS code just to assist with behind the scene operations and to secure the single operating certificate.
It will make their entry into ONEWORLD easier now.
For now, the service and branding remains separate, and eventually they will share the same service and some AS FAs will train for 787 operations, but for now, only Hawaiian F/As can work their own current fleet of A321 and A330s and of course Boeing 717s.
I can imagine them launching new cabin and catering service next year, but given how they can't even introduce a new international service on these Seattle to Japan/Korea flights by now, I don't think you need to worry about Hawaiian cancelling the current meal services yet. March might be okay, but summer might be a different story though.

Carfield