Jason at National Post is saying that Feist may play at the festival in a few weeks.

Kevin Drew, Brendan Canning, Amy Millan, et al. will take the stage to close the festival on Sunday, July 27, honouring one of the venues that originally helped put them on the Canadian musical map.

[...]

All we can be left to wonder now is whether Feist [...] will join her old bandmates at Ontario’s premier hippy love-in
— Broken Social Scene to break hiatus for Guelph’s Hillside Festival 27 Jun 2008

The post also speculates about whether Arcade Fire will play on Saturday.

Regardless, I plan to be there and hopefully I will get mobile connectivity to be able to report directly from the pen-island.

• Weekend on the island in a lake 31 Jul 2007