FSR 4 has been in development for 9-12 months already, and one of the biggest focuses is improving battery life for handhelds - eviltoast
AMD plans for FSR4 to be fully AI-based — designed to improve quality and maximize power efficiency
www.tomshardware.com
The team in charge has already been working on this for 9–12 months.

He specifically cited bad battery life on the ROG Ally and Lenovo Go, saying that getting only one hour of battery life isn’t enough. The Steam Deck (especially the OLED model) does a lot better battery wise, but improving power efficiency should really help with any games that are maxing out the Deck’s power.