I beg to differ. The phrase in this world or in the next is to emphasize the fact that blaspheming the Holy Spirit is absolutely unforgivable not to imply that there is a holding pattern for the not-quite-holy-enough to finally get their spiritual act together.
and the Church for 2,000 years has called this state purgatory
The early church started out preaching the shed blood of Christ for the forgiveness of sin. That's what Jesus talked about. At the last supper, I'm sure he didn't say, "...and if My body and blood aren't quite good enough, there's always purgatory..."
By the way, how does one get out of purgatory?
You misunderstood. For those in purgatory, their sins are forgiven. The Blood of Jesus is applied to them. But the temporal punishment for these sins that is left is what is being repaid there.