You would wonder whether your current visa status is valid or not if the date of expiry of your current visa status is expired while you have applied for Extension of Period of Stay (or Change of Visa Status) and the application is still in progress at the Immigration Office.
Getting straight to the point, your current visa is valid during the EXCEPTION PERIOD / 特例期間 (Tokurei kikan) if your application has been filed at the Immigration Office and it is still in the progress after the date of expiry stated on your current Residence Card. You can even travel outside Japan and reenter Japan under your current visa status during the Exception Period / 特例期間 (Don’t forget to obtain Special Re-entry Permit when you depart from Japan).
For further details, please check EXCEPTION PERIOD / 特例期間 on our web page below;
In addition, here is a web page of the Immigration Office explaining this 特例期間 (exception/special period) of 2 months >> https://www.moj.go.jp/isa/applications/procedures/tokureikikan_00001.html
* You can change the language on the Immigration Office’s website or utilize Google Translate.
Of course, for the safety, it is much better to pick up your new Residence Card at the Immigration Office before your departure and travel outside Japan with the new card in case you receive the notice of approval (a postcard, or email in case of online application) from the Immigration Office.