As non-PIGS nations leave, the non-PIGS nations still left will be incentivized to leave even faster. Eventually it will be PIGGS, That is, the PIGS and Germany. :D
I think the good people of Poland have good reason to leave.
The PIIGS term made sense only in 2014.
Since then
1. Ireland has been growing fast
2. Spain has recovered since 2017 and is growing
3. Portugal has recovered since 2018 and is slowly growing
4. Greece is stable
5. Italy is somewhat stable
Spain was growing twice as fast as the US in 2017, Ireland is similar, Portugal is doing fine. Italy a bit less but not doing terrible either. The only real problem child is Greece
As to “the EU’s collapse” - that will happen one day eventually, but none of those going rah-rah give any alternative for what to do then.
The countries of the EU bar Germany and France and to some extent Italy, are too small to really stick around well by themselves - they would be bullied by bigger players.