Archiving annual festival site

I have a query regarding managing a wordpress setup, I am sure others have been in a similar situation and was wondering what would be the best solution.

I manage an annual festival’s website, each year has a different theme / design and event details, this is archived each year [ ie at festival.com/2008/ etc.]

Last year we moved to a wordpress platform and all was good, now have a new theme for this years festival and the new event details ready to go but I have a dillema…

Is it possible to have one wp blog with an archive of last years festival ie 2010 theme and 2010 events/pages accessed via festival.com/2010/ and this year events/pages and theme show up when visiting the main site [ ie festival.com/ ]

so i need one blog with multiple themes and event filtering

I can filter event/page by a year category but will this mess the menus etc.
or am i best off just moving the existing wp install to the festival.com/2010/ directory and creating a new blog and in the site root [ festival.com] ?

any suggestions, advice or pointers would be great,

Thanks in advance,

Keith