since the rumor was 12” MB, not MBA, fanless seems like a given (the old MB was also fanless, and apple silicone is much cooler than intel’s garbage).
as for faceid, who knows. Touch ID works pretty well, and you‘d still have to touch something to authenticate after initial authentication (i.e. for purchases or whatever), so not as much benefit on a mac as on a phone.
5G? Again, maybe. It’s certainly been lacking, and it would seem a bit weird if you could get 5G on an ipad but not on a MB running with essentially the same architecture but costing more.