CSGO has been with the same engine and UI since launch. To many, including me that has been a sticking point in the development of CSGO. We have not seen any UI interface overhaul since 2012.
Valve, while announcing the launch of CSGO in China also announced the launch of CSGO on the new Source 2 engine in Summer. While the announcement has not been made in English and we do not see any possible news or information about the upcoming operation.
Operations in CSGO are extremely important in the sense they provide a break from the routine gameplay and maps pool. The community definitely loves to play on the operations. The last operation was released almost a year ago.