Currently HTC is the only company that does not have a line of tablets and might have plans to come up with their line of tablets this or the next year. According to @evleaks HTC has plans to come up with their own tablets including the Nexus that that we have been hearing rumors about though there is no confirmation from Google or HTC if they are working on one.
The rumors regarding Nexus 8 have been there for a long time but we are sure that there won’t be any news about its launch till Google launches its new operating system code named Android L, after which we will know if Google has plans to launch a Nexus tablet or not. According to some other sources the upcoming Nexus tablets might have a 9 inch display which means that Google will end up calling its Nexus 9 instead of Nexus 8, though various code names about the new Nexus tablet have been seen including Flounder and Volantis from HTC.
Other than the new Nexus tablet HTC is also said to come up with their own two tablets with model number T7 and T12 and the number of these models might represent the screen size which would make it a 7 inch tablet for the T7 and a 12 inch tablet for the T12, but that might not be correct as the model number for the Nexus tablet is said to be T1.
If Google chose HTC to be the manufacturer of their next Nexus tablet then we should expect a good tablet with maybe a metal body and BoomSound speakers. HTC Volantis is also rumored to be equipped with a 5GB of RAM which would be more than enough to run Android L and all the new animations and effects that the UI has to offer.