In an announcement on their website, First proudly boast that all buses will have coach style seats, free WiFi (with hopefully more data allowance than the current ridiculously small amount), USB charging at all seats, seat back phone docks with wireless charging, and bus stopping buttons at every seat. They hint at other features which are still to be revealed. You can read the full announcement here.
I have no pics as present, although a few are doing the rounds on Facebook, but can say the livery is similar to the new red livery being rolled out around the country. What distinguishing extras the excels will have is to be seen. I just hope the Scania chassis proves to be sturdier than the ADL chassis. I've been on a couple of 2yo Citis in London recently and the body noise was horrific - even a driver said it gave him migraines. So when First say "build quality, ergonomics and style are all integral to the Alexander Dennis bodywork" you'll have to excuse me for sitting firmly on the fence for a few months!
There will no doubt questions as to what's happening to the current fleet on the XL. As far as I know they will be transferred to Lowestoft for use on the X2, with the current X2 Volvo B9's going to Norwich for the Orange Line, amongst others which should see the end for the final Presidents there.
The new buses are scheduled for entry into service "Spring 2020", which could mean anything between February and May, I guess. The obvious direct contrast will be the new Optare Metrodeckers being built for Greenline 702, which will enter service at roughly the same time. I want to be pleasantly surprised. Time will tell.