In reality - I think this pandemic and quarantine will lead to break downs of a lot of relationships, rather than affairs.
Affairs are already not based on daily contact and if that contact is interrupted, they’ll just hibernate and reunite when possible. And spend time jointly fantasising about it.
However - the real day-to-day relationships that aren’t well functioning, with lack of good communications, or intimacy issues - those will be severely strained in the days of seeing each other 24/7 and running each other the wrong way. Prior to now - work has provided escape for many, and so did affairs.
So while reconnection with the spouse may happen to few - to many this time can just be the last straw.
And once this is over and people realise how short and precious life is - and that it can’t be taken for granted and there isn’t an unlimited time for things to get better - I think there will be a huge fall out.