And only to clarify, gmail and drive does count against your 15gb, the big change is that now your photos will count as well. Pixel 3 owner is still free till Jan 2022, and pixel 4/5 is free unlimited.
To clarify the clarification.
Pixel 3 has unlimited
original quality till Jan 2022. After that unlimited high quality.
All Pixel phones currently on the market will not be affected by the changes and will have unlimited high quality storage.