According to an Ada Derana article dated 7 January 2020, the Central Bank of Sri Lanka plans to introduce a new 20-rupee coin and a new 2,000-rupee note (current B120a shown above) in 2020 to commemorate its 70th anniversary. Additionally, security features of the existing banknote series will be enhanced.
It is best to quote the original CBSL statement in their 2020 roadmap which is
Marking its 70th anniversary, the Central Bank is planning to issue a commemorative coin of Rs. 20 and a new currency note of Rs. 2,000 under the existing 11th note series in 2020. Security features will also be further upgraded in the existing 11th currency notes series.
https://www.cbsl.gov.lk/sites/default/files/cbslweb_documents/press/pr/press_20200106_road_map_2020_e.pdf
The Rs2000 would be in current Series with Birds and drummers. Not the old Series shown in post.
Has this commemorating note never been issued?