All four initial configurations of the 14in MacBook Pro (both colors, and with 8- and 10-core CPUs) offer delivery rates of 2-9 December via Apple UK store view at the time of writing.
But for once UK consumers are going smoothly compared to their transatlantic friends. At the US Apple Store, delivery times are even longer, with customers warned not to expect delivery until the beginning of January.
Leaving high demand on almost any new Apple product (which is predictable), one possible reason for the long delivery times is the global shortage, which is rampant in the electronics industry at the moment. So it is not necessarily the case that the new models are in greater demand than their predecessors.
On a related note, there are longer lead times for other Apple products at the moment, including the iPhone 13, iPad and Apple Watch. There are fears, indeed, that widespread Christmas shortages could make up for the time of unprofitable deals, with more demand than supply and retailers therefore under low pressure to significantly reduce.