From what I recall, those tests were said to merely involve upscaling the SD tapes to see if they could "get away with it". I'd be surprised if they met with any great success.
Get away with it?!
I just watched TNG Episode #252 'Descent: Part I' last night on DVD on a 26" standard def. TV. It looked pretty soft and bad to me. Not just the darkly lit Borg ship but the brightly lit TNG Enterprise-D closeups on Patrick Stewart.
There is no way they are gonna upscale the video from those masters and pass it off as HD on a Blu-Ray. TNT does that on their TNTHD channel and also stretches 4:3 standard def. content. It's one thing when a broadcaster fills time with a non-HD show but for Paramount/CBS to try to _SELL_ a product that has been sold to fans on VHS and DVD already from those videotape masters dating back to 1987.
It will either live on DVD as seasons like ST:Voyager always will or they will start with fan collective sets first to gauge customer interest in HD Blu-Ray purchases of TNG.
Also Blu-Ray is still a new format. It was only in January of 2008 that the format was considered THE next consumer video format as HD. In 2009 they will release most of the feature films and ST:TOS on Blu-Ray all in HD.
If they do decide to do it that probably wouldn't be on a store shelf for 18 months. In the mean time they will release TOS seasons 2 & 3 probably in 2010.