At least one of the four expected variants of the upcoming Samsung Galaxy Note 10 phablets will come with a 4500 mAh battery, according to an image of a battery found on a consumer website for South Korean KC certification. At almost the same time, it has been reported that the same device will also support fast 25 W charging.
https://www.notebookcheck.net/Fresh-Samsung-Galaxy-Note-10-leaks-4500-mAh-battery-25-W-fast-charging-model-numbers-deciphered.419727.0.html
Coming from a Note 8 with a conservative battery capacity this looks like it'll be my next device.
Finally actually fast charging. 15W hasn't been too fast from my experience with Galaxy phones.