Category 5E is the highest-performing UTP cable that is governed by a ratified standard. So-called Category 6 wiring products are emerging, but the standard has not yet been approved (it exists in draft as TIA/EIA-568B.2-1, Draft 7a).
Manufacturers are banking on the proposed 250-MHz Cat 6 standard being adopted soon and are basing product lines on that assumption. As with Cat 5E UTP, we'll see wildly varying performance ratings on wiring products labeled Cat 6. A 250-MHz Category 6 wire is available from SouthWire, while CommScope markets both a Cat 6 (400 MHz) and a Category 6e+ (550 MHz) wire.
Truly adventurous vendors are marketing some form of Category 7 wire. The Cat 7 standard is barely in its infancy, but it's expected to end up as either 600-MHz or 700-MHz UTP when and if it reaches completion.
Although bandwidth capacity alone doesn't sell UTP products, other performance measurements tend to run so close among competitors that bandwidth variations jump out as the differentiating "feature" of UTP products.