website shows the tuners. only available for the HD units.
the base units for the hd-4/5xxx have external tuners. T430/T410 for the hd-4xxx. T530/T510 for the hd-5xxx.
the base hd-4xxx has a slot above the fan. this is where its tuner would insert. it's separate, so you have to buy it separate.
the tuner for the hd-5xxx (T530/T510) is a round disc shape; the hd-5xxx unit sits on top of it. it connects to the usb-host port. again, it's separate, so you'd have to buy it separate.
the multi-i/o port that the hd-5xxx has seems to only have one use right now -- "breakout box" that just has extra av outs. doesn't seem necessary. perhaps they'll make more addons for this port in the future.
the website also shows an upgraded version of the hd-5000, which has the tuner built in. apparently, there's also an upgraded version of the hd-4000 with a built in tuner as well, but there's no page on it; it only says in the comparison table. since they're upgrades of the hd-4/5000, they don't support sata HDDs. doesn't matter much to me because it doesn't seem like they will be sold. i'd have to get the base unit and tuner separately.
also seems like there will be an upgraded hd-5100 with built in tuner as well. could be a typo, but doesn't look like there will be an upgraded hd-4100 with a tuner. again, either way, they probably won't make it to the states.