Hi, I would say high or higher end would be a TiVo that has additional hardware or software features that their entry level boxes do not have. So yes I do expect the Series 3 to be a higher end device, because I am still assuming there will be something like the current Series 2 available also.
But I still not sure if the series 3 will be a high end media center or not. A media center needs to be able to access, store, organize, edit, and display photos, music, and video. If you take a look at the D-Link mediaLounge current and upcoming products you start to see some of this coming together (they still need work also). But they have some things TiVo could use like built in WiFi, built in picture card readers, ability to read and write USB Flash drives, ability to handle many video and music formats, plus additional Internet services.
Of course the more hardware or software features you have the more it costs. Which is why I think it is time for TiVo to have a line of DVRs, enter level to high end. The high end media center DVRs may actually be full power computers and have very high costs, which is fine TiVo needs products for people to move up to when they have more money, just like the TV manufactures, most have $2-300 enter level TVs and build product lines up to $5-6000 large screen HD TVs.