My Mac running Snow Leopard has several MacPorts based open source software packages installed. Upon the upgrade to Lion, all my ports are listed as outdated.
It's safe to upgrade them en masse?
I usually don't upgrade to a new major version of OS X until MacPorts has released their first official support for it.
I agree with Jerry Jacobs that you should probably back up your
/opt hierarchy before attempting. Then you could try doing
sudo port selfupdate to see if that upgrades you from 1.9.2 (or whatever) to the 2.0.0 release candidate. If it does, then you can try
sudo upgrade outdated.
I wouldn't try doing a
sudo upgrade outdated on Lion without at least being on the 2.0.0 release candidate of MacPorts.