Future performance issues on mac?

Drakilian

64-bit Client
We’ve introduced a 64-bit version of ESO for the Mac game client, which will automatically open from the ESO launcher if you have a 64-bit compatible OS.

• This will fix a large number of crash issues, as well as improve memory usage.
• The Mac client will now require more RAM, with 8GB of RAM recommended.
  • Machines with 4GB of RAM may see a negative effect on game performance.
• Only the 64-bit version for the Mac client will be supported moving forward.
• The 64-bit client for the PC client will be available in a future PTS incremental patch.

Now, when you say they may see a negative effect on game performance, just HOW negative are we talking here?