There are 3 major issues Shaw Direct has to address to provide a 4K service - bandwidth, hardware and content.
Bandwidth - they are in the midst of converting SD to HD MPEG-4 and removing SD duplicates, which should be complete by 2019. See:
Hardware - Shaw Direct is in the unique position of developing their own hardware, which includes new hardware capable of handling 4K. I think the next PVR they develop will be 4K-compatible, but who knows when that will be. Most other Canadian providers use commercially available hardware from third parties (although Rogers and Bell Fibe were on the bleeding edge in working with their hardware providers.)
Content - Most 4K content is limited to specific Canadian home games on TSN and Sportsnet - NHL, MLS, Blue Jays and Raptors. Don't expect American series anytime soon, although Bell Media has committed to producing all new Canadian series in 4K. There are also a handful of 4K movies available for rental.
I wouldn't expect anything before 2019, if ever.
In addition to Rogers, Bell Fibe TV, Bell Aliant, Telus Optik TV and Videotron all offer 4K. Noticeably absent is Shaw Cable because their supplier (Comcast) isn't ready to make the move.