I believe the draft was held over one day for most of its history, even when it was 11 and 12 rounds. (Except for that one conference call draft in the mid 70s which took several days). The first two-day draft that I can remember is 1994 in Hartford, when they had to work around a PGA stop in the city at the same time.
Can't remember when it went to two days, but it was held over two days for quite a few years. Last year was, of course, a one-day draft.
The last thing we need is the entire draft on TV. It's pointless. I could understand expanding coverage into the second round, but after that, nobody's heard of anyone being drafted. The networks wouldn't pick it up. How do you sell advertising for the fifth round of the draft?
The NBA Draft is only two rounds. That's pretty damn easy to televise. A classic apples vs. oranges argument.