For the last year and a half I've been making and exhibiting 5x7 foot (60"x86") prints made on a Canon iPF 9100. I have them stretched on 2.25" deep custom made stretcher bars for about $150 (pricing at this size are usually double this). I consider this to be about the largest *reasonable* size canvas inkjet prints that common users can expect to make. While many RIPs can make longer prints (and the Canon iPF print plug-in allows prints up to 708 inches (59 feet) without a RIP) having them stretched or attached to panels is problematic. It would be easier to tile larger images onto multiple prints, stretch them separately and display them together as a diptych, tryptic, etc. FYI, whenever you stretch canvas around stretcher bars one needs to consider the image area that goes on the sides and plan your tiling overlap areas carefully when tiling an image into several smaller prints.
I'm not aware of any canvas materials that are available in rolls larger than 60/64 inches. Stitching strips of canvas together would be problematic - I doubt you could find anyone that would be willing to even try this for you. If you want to go larger than this I would consider looking into signage printers as Henrik mentioned. I've done a fair amount of color management consulting with signage printers over the past 15 years so I'm pretty familiar with the technology. In fact, it's my curiosity with grand format printing at these client's shops that has brought me to acquiring a 9100 for printing my own fine art work. Some signage printers (like the Scitex XLjet) are sixteen feet wide and at these extremely large sizes, printing on vinyl is the norm because of it's availability, affordability, durability and handling characteristics. Signage print vendors use hot air "welding" machines to melt half inch overlaping strips of vinyl to each other. With this technique I've seen my clients wrap 20 story buildings on all four sides. The limits are constrained to one's budget.
I've long encouraged artists not to overlook using these signage printers for their work. While the dot size is much larger (~4 picoliters) than we are used to with inkjet (~1.5 picoliters), so are typical viewing distances for large work. While printing resolutions for these signage printers used to be stuck at 600 dpi, they are now creeping up to 1040-1440dpi range When combined with 8-16 passes and 4+ inksets, the effective visibility of printer dots is quite low. Accuracy of dot placement is also another area that has just recently improved dramatically - some of these machines can now render 4 point type with excellent readability. The color gamut of solvent printers is particularly fantastic and may eventually steal away market share from todays pigment printers.
Also of note are UV-curable printers that signage print vendors also have. The color gamut isn't as wide as solvent printers but they are capable of printing onto just about anything. I've seen some pretty nice artwork printed directly onto large sheets of foamcore, aluminum, wood and even glass at surprisingly low all-inclusive costs.
As photographers, we have replaced our silver gelatin tunnel vision with inkjet tunnel vision and it can be really fun to break-out and try something different. Good luck with your venture into grand format printing!
P.S. Straight forward grand format printing can be disappointing even with with 50+ megapixel source images. Enhancing localized contrast and adding subtle amounts of noise are common keys to satisfying grand-format prints and the techniques for this are worthy of a whole other lengthy discussion.