There will be 4G in Canada eventually, but our 3G on all the networks are as fast or faster than the 4G speeds in the US. Sprint and Verizon are really pushing the 4G because they're using CDMA which is very slow compared to T-mobile and ATT's HSPA. And not wanting to appear to be left behind, they're all marketing it as 4G when it's really not.
The Canadian carriers will most likely be more pragmatic about upgrading. They'll wait until they get the same spectrum the US will be using (700MHz). It'll be freed up this summer when analogue tv broadcasts are shut off and the auction sometime in 2012. Then it'll be another year or two before you see real phones with LTE.