HTC doesn't have a very successful history with tablets. It's 7 inch HTC Flyer and 10 inch HTC Jetstream, launched in early and late 2011 respectively, both failed to catch on with buyers despite the HTC Scribe technology, which used a stylus as a pen and was ahead of its time. HTC sold the pen separately for $79.99, a move which didn't exactly promote sales of its tablets.
Speculation is that Google turned to Asus to produce the Nexus 7 after being turned down by HTC. After seeing how successful that slate turned out, HTC has purportedly been given a second chance with the Nexus 10, and based on the rumor, won't make the same mistake twice. Of course, until we hear from HTC that it is going to make a refreshed Nexus 10, you should take this information with a grain of salt.