According to Wikipedia the individual battalions will retain their old uniforms for their individual pipes & drums.:
"The Royal Regiment of Scotland is the senior and only Scottish line infantry regiment of the British Army Infantry. It consists of five regular and two territorial battalions, each formerly an individual regiment (with the exception of the first battalion, which is an amalgamation of two regiments). However, each battalion maintains its former regimental Pipes and Drums to carry on the traditions of their antecedent regiments."