Volume seem to have reached a plateau on most
poker sites and will likely begin to slowly decline again at some point. How fast that decline will be, is difficult to say. It seems likely now, that there will remain limitations on many of the recreational activities, that compete with online poker, for quite some time.
There will for the foreseeable future be no sports events, concerts or festivals, and in many countries bars and discos will remain closed. There will for sure be way less travel than normal. So even if people go back to work, they will still have less to do in their free hours.
Game quality has probably also peaked. I feel, I see some signs of that on PokerStars already. This is also a natural development, because the money transfer from bad to good players, and the bad players then either stop playing or start to study and become better.
As I wrote before, the economic crisis is also not good in the long run for any kind of business, who deliver non-essential services or goods. Right now people still have money, but that is going to change in the not so distant future, as more and more people lose their job and income.