While it's true that interline averaging reduces vertical res by around 30% it has another advantage, it reduces noise, this can't be done in progressive scan so you pay a penalty in reduced low light performance, the DVX100 was according to Panasonic a good example of this trade off.
Not that I'm any fan of interlaced video, I've spent too much of my life wrestling with the problems that it causes, I'll be glad to see the end of it.
I think we're going to see some interesting developments in video technology, I've recently been looking at cameras that work at the cutting edge using CMOS sensors capable of 1000fps and beyond, the technology is there to build one heck of a 'Varicam', the data storage requirements are daunting but achievable.
Bob.