https://www.jal.co.jp/en/info/inter/190611.html
First phase will start Jul 1 2019, expected completion date is Oct 2019. Sakura Lounge SKYVIEW will be closed and JAL will provide access to SKY LOUNGE ANNEX, the paid lounge downstairs. Of course you can access the main Sakura Lounge.
First Class lounge will also be renovated before Mar 2020. Unclear whether the main Sakura Lounge will be closed for renovation or not.