When will we get more Big Sur updates?

Possibly never. Apple normally provides security updates for the current and two prior macOS versions. See: Apple security releases - Apple Support

Also note that Big Sur is the latest compatible macOS for a 2014 MacBook Air. See the following from Identify your MacBook Air model - Apple Support

MacBook Air (13-inch, Early 2014)

Year introduced: 2014

Model Identifier: MacBookAir6,2

Part Numbers: MD760xx/B, MD761xx/B

Newest compatible operating system: macOS Big Sur

No one here can answer that. It may get security updates, but it is technically outside of the support window. Only the 3 most current versions of macOS are supported.

Thankfully Safari isn't the only browser that is available for Big Sur. There are many more current browsers.

Browsers by Mac operating system - Apple Community