I guess, you are right. Looks like there will be an option of installing Rosetta in 10.6 but no uninstall because it is part of the OS (see http://www.apple.com/rosetta/).
You would probably need a reinstall of the system as you rightly guessed.

Alex
3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN