Hi Soeren,
While it is true that the default page size has changed to 4k, the only way to really tell if you would gain performance by switching from 2k to 4k pages would be to benchmark your system under both settings.
To move to 4k pages, you can use the Sybmigrate utility. It will take longer than loading a dump.
But you also don't have to do it as part of the upgrade, it can be used later.
-bret