Notes, saved places and reservations will still exist in search as long as you sign into your Google account. You'll "soon" have the option of adding or editing notes through the search site's travel portal. you'll also find things to do, saved places and (in the near future) trip reservations in the Maps app, and your bookings will automatically become available offline.
The switch-up is unfortunate if you liked having all your vacation info in one place. However, it's not hard to see why Google might shutter Trips three years into its existence. Many of its once-special features are now available in a web browser or the Maps app you likely already have on your phone. There's not much incentive to devote resources to a specialized app, especially when search and Maps offer more tools for adventurers.