The Canada Revenue Agency (CRA) is cutting back this year ("reducing waste," they say), and they're not automatically mailing out income tax packages to everyone who filed a return last year. They're encouraging as many people as possible to file online. They've also discontinued the TELEFILE program and the related Service for Seniors program which let people with simple tax returns file by phone.
You can still get a paper tax package though. Where to Get a Canadian Income Tax Package tells you how to download one online (they're available now), order one online or by phone (they won't be mailed until February 4) or pick one up in person at a postal outlet or Service Canada office starting February 4.