Well, I had a 60 meg test cable connection with TekSavvy for two and a half years, it worked perfectly fine :P Well, after the upstream got bumped up high enough (it sucked at the 1 and 2 meg upstream levels)
It's a TekSavvy policy issue, rather than a technical issue; TSI can order a 60 meg cable line, they just choose not to. My guess is that they didn't have much interest in offering it before, and at this point, they're looking into the costing to see what pricepoints they need to offer it at.