Question about Apple iPhone 15 Pro

I've been using an Iphone7 with 128 GB since 2017, 67 GB of which is still available. I make few calls and manage very well with 1 GB of data per month. It's the ideal size for me and the successor product shouldn't be any bigger (easy to stow in my trouser pocket). I would like to use the successor model for as long as possible. Which model with which features would you recommend? Thank you very much