Wait for Improved Performance
Apple is reportedly planning to install new chips inside the 2020 iPhones. Not that that comes as a surprise.
According to the hit-or-miss Digitimes, "TSMC is expected to secure the first 5nm chip orders from Apple for the 2020 iPhones."
TSMC recently confirmed the release of its complete 5nm chip design infrastructure paving the way for next year's A14 processor.
If you aren't thrilled with the battery life and overall performance on the current crop of devices, think about waiting.